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  • Blackwell Science Ltd
  • 2005-2009
  • 1995-1999  (1,507)
  • 1999  (1,395)
  • 1995  (112)
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  • 2005-2009
  • 1995-1999  (1,507)
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  • 1
    Electronic Resource
    Electronic Resource
    The product of the pilQ gene is essential for the biogenesis of type IV pili in Neisseria gonorrhoeae (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The product of the Neisseria gonorrhoeae omc gene possesses regions homologous to those found in members of a protein superfamily that are associated with the translocation of proteins and DNA-protein complexes across the outer membrane. Amongst its protein homologues, Omc has higher overall homology to PilQ, which is required for type IV pilus expression in Pseudomonas aeruginosa, and OrfE, which is required for sequence-specific DNA uptake by Haemophilus influenzae. The function of Omc, however, is unknown and gonococcal omc mutants have not been described. We constructed gonococcal mutants expressing truncated forms of the protein, and found that these mutants are severely defective for both pilus expression and competence for natural transformation. To be consistent with pre-existing pilus gene nomenclature, we have redesignated the gene pilQ instead of omc, and its product, PilQ instead of Omc. The MS11 gene was sequenced and found to differ from the DNA sequence reported for that of another gonococcal strain; these differences were associated with a repeated DNA element, suggesting a genetic basis for structural variation in PilQ. The results also show that PilQ− mutants are distinct from previously described gonococcal pilus-assembly mutants and P. aeruginosa PilQ− mutants by virtue of their expression of rare pilus filaments. Taking these data into account, PilQ is proposed to function in the terminal steps of organelle biogenesis by acting as a pilus channel or pore.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.18050975.x
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  • 2
    Electronic Resource
    Electronic Resource
    Similarities between the lethal factor of Bacillus anthracis and leukotriene A4 hydrolase (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.18050991.x
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  • 3
    Electronic Resource
    Electronic Resource
    Photonic detection of bacterial pathogens in living hosts (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The study of pathogenic is often limited to ex vivo assays and cell-culture correlates. A greater understanding of infectious diseases would be facilitated by in vivo analyses. Therefore, we have developed a method for detecting bacterial pathogens in a living host and used this method to evaluate disease processes for strains of Salmonella typhimurium that differ in their virulence for mice. Three strains of Salmonella were marked with bioluminescence through transformation with a plasmid conferring constitutive expression of bacterial luciferase. Detection of photons transmitted through tissues of animals infected with bioluminescent Salmonella allowed localization of the bacteria to specific tissues. In this manner progressive infections were distinguished from those that were persistent or abortive. We observed patterns of bio-luminescence that suggested the caecum may play a pivotal role in Salmonella pathogenesis. In vivo efficacy of an antibiotic was monitored using this optical method. This study demonstrates that the real time non-invasive analyses of pathogenic events and pharmacological monitoring can be performed in vivo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.mmi_18040593.x
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  • 4
    Electronic Resource
    Electronic Resource
    The effect of receptor rapid-internalization signals on diphtheria toxin endocytosis and cell sensitivity (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Diphtheria toxin enters toxin-sensitive mammalian cells by receptor-mediated endocytosis employing the heparin-binding EGF-like growth factor precursor as its receptor. We reported previously (Almond and Eidels, 1994) that cytoplasmic domain mutants of the toxin receptor and cells expressing wild-type receptor internalize toxin slowly, the rate being approximately that of normal turnover of the plasma membrane. To determine whether it was possible to increase toxin sensitivity by increasing the rate of toxin internalization, we constructed diphtheria toxin cytoplasmic domain mutant cell lines containing rapid-internalization signals from either the low density lipoprotein receptor or from the lysosomal acid phosphatase precursor. Although cells transfected with mutant receptor genes internalized toxin at a faster rate than those expressing the wild-type receptor, they showed a decrease in toxin sensitivity. This decreased sensitivity may be accounted for by an observed decrease in the number of toxin-binding sites and by an increased rate of toxin internalization and degradation. These results suggest that the rate of toxin internalization may not be the rate-limiting step in the cytotoxic process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.mmi_18040623.x
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  • 5
    Electronic Resource
    Electronic Resource
    Benefit of transcription-coupled nucleotide excision repair for gene expression in u.v.-damaged Escherichia coli (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Expression of the lactose operon upon induction by IPTG was studied with Escherichia coli B/r and K-12 strains as a function of exposure to ultraviolet light. Patterns of expression inactivation were compared in cells with wild-type UvrABC nucleotide excision repair, with transcription-coupled excision repair (TCR) specifically defective because of a defect at mfd, or with excision repair (ER) and TCR eliminated by defects at uvrA or uvrC. Sets of inactivation patterns were also determined for cells expressing the lactose operon via the ‘UV5’ promoter, an alternative to the wild-type promoter that eliminates dependence of expression on negative DNA supercoiling. The results demonstrated a major contribution by TCR to successful gene expression. Gene expression was more sensitive to u.v. inactivation when TCR was defective and similarly more sensitive when both ER and TCR were defective. Thus, TCR may be the only means of repairing transcription-blocking damage at active genes. Contrasting results with wild-type and UV5 promoters suggested that relaxed supercoiling might accompany repair and reduce expression even though a template lesion is removed. A test of mismatch repair defects on ultraviolet inactivation of gene expression found only limited interference with TCR as it benefits gene expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.mmi_18040615.x
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  • 6
    Electronic Resource
    Electronic Resource
    Organization of the Saccharomyces cerevisiae actin gene UAS: functional significance of reiterated REB1 binding sites and AT-rich elements (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The upstream activation sequence (UAS) in the Saccharomyces cerevisiae actin gene promoter contains three different motifs, specifically two AT-rich tracts, two binding sites for the yeast protein REB1, and an Mlul site. Synthetic UAS elements containing individual motifs, or combinations of them, were inserted in place of the natural UAS, and assayed using a lacZ reporter gene. The REB1 binding sites were found to be essential for, and sufficient to restore partial, UAS activity. AT-rich tracts alone were inactive. Multimerization of a REB1 binding site created a UAS that in galactose is more active, but in glucose less active, than a UAS having a single REB1 site with one AT-rich tract. In general, transcription during growth in galactose or glycerol/lactate responds more to multimerization of motifs. The results suggest that the natural actin promoter UAS retains activity on these alternative carbon sources because of reiteration of sequence elements within it; the additional elements appear to be redundant when cells are grown on glucose. The mlul site, which is present upstream of a number of yeast genes involved in DNA synthesis and confers cell cycle periodicity to those genes, contributes to the activity of the synthetic UAS elements, but not in a cell-cycle-dependent manner.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.mmi_18040605.x
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  • 7
    Electronic Resource
    Electronic Resource
    Regulation of anaerobic citrate metabolism in Klebsiella pneumoniae (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Three enzymes are specifically required for uptake and catabolism of citrate by Klebsiella pneumoniae under anaerobic conditions: a Na+-dependent citrate carrier (CitS), citrate lyase (CitDEF), and the Na+ pump oxalo-acetate decarboxylase (OadGAB). The corresponding genes are clustered on the chromosome, with the citCDEFG genes located upstream and divergent to the citS—oadGAB genes. We found that expression of citS from its native promoter in Escherichia coli requires the DNA region downstream of oadB. Nucleotide sequence analysis of this region revealed the presence of two adjacent genes, citA and citB, By sequence similarity, the predicted CitA and CitB proteins were identified as members of the two-component regulatory systems. The sensor kinase CitA contained, in the N-terminal half, two putative transmembrane helices which enclosed a presumably periplasmic domain of about 130 amino acids. The C-terminal half of the response regulator CitB harboured a helix-turn-helix motif typical of DNA-binding proteins. K. pneumoniaecitB null mutants were unable to grow anaerobically with citrate as the sole carbon and energy source (Cit− phenotype). When cultivated anaerobically with citrate plus glycerol, all of the citrate-specific fermentation enzymes were synthesized in the wild type, but not in the citB mutants. This showed that citS, oadGAB and citDEF required the CitB protein for expression and therefore are part of a regulon. In the wild type, synthesis of CitS, oxalo-acetate decarboxylase and citrate lyase was dependent on the presence of citrate, sodium ions and a low oxygen tension. In a citA null mutant which expressed citB constitutively at high levels, none of these signals was required for the formation of the citrate fermentation enzymes. This result suggested that citrate, Na+, and oxygen exerted their regulatory effects via the CitA/CitB system. In the presence of these signals, the citAB gene products induced their own synthesis. The positive autoregulation occurred via co-transcription of citAB with citS and oadGAB.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.mmi_18030533.x
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  • 8
    Electronic Resource
    Electronic Resource
    Identification of a plasminogen-binding motif in PAM, a bacterial surface protein (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Surface-associated plasmin(ogen) may contribute to the invasive properties of various cells. Analysis of plasmin(ogen)-binding surface proteins is therefore of interest. The N-terminal variable regions of M-like (ML) proteins from five different group A streptococcal serotypes (33,41,52,53 and 56) exhibiting the plasminogen-binding phenotype were cloned and expressed in Escherichia coli. The recombinant proteins all bound plasminogen with high affinity. The binding involved the kringle domains of plasminogen and was blocked by a lysine analogue, 6-aminohexanoic acid, indicating that lysine residues in the M-like proteins participate in the interaction. Sequence analysis revealed that the proteins contain common 13–16-amino-acid tandem repeats, each with a single central lysine residue. Experiments with fusion proteins and a 30-amino-acid synthetic peptide demonstrated that these repeats harbour the major plasminogen-binding site in the ML53 protein, as well as a binding site for the tissue-type plasminogen activator. Replacement of the lysine in the first repeat with alanine reduced the plasminogen-binding capacity of the ML53 protein by 80%. The results precisely localize the binding domain in a plasminogen surface receptor, thereby providing a unique ligand for the analysis of interactions between kringles and proteins with internal kringle-binding determinants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.mmi_18030569.x
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  • 9
    Electronic Resource
    Electronic Resource
    Uptake of inorganic carbon in the cyanobacterium Synechocystis PCC6803: physiological and genetic evidence for a high-affinity uptake system (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Synechocystis PCC6803 displays two inorganic carbon-uptake processes, a low-affinity one (apparent Km: 300–400 µM) functional in cells grown under standard or limiting inorganic carbon concentrations, and one with a higher affinity (60±12 µM), detected only in cells adapted to limiting inorganic carbon conditions. A mutational and screening procedure allowed the isolation of a mutant deficient in the high-affinity system, but only slightly impaired in its growth capacities. The mutated genomic region revealed two open reading frames (ORFs), possibly belonging to an operonic structure. A clone in which the downstream ORF, hatR (high-affinity transport), had been inactivated showed a phenotype close to that of the original mutant. Inactivation of the other ORF, hatA, yielded a clone unable to grow in limiting inorganic carbon conditions. The deduced HatA protein showed no homology with any registered protein. It possessed three hydrophobic domains, including a putative signal peptide. Several hypotheses are considered as to its role. The deduced HatR protein, which possessed the features characteristic of the response regulators of the two-component regulatory systems ubiquitous in bacteria, might be a regulator controlling the activity of the high-affinity transport process. It would belong to the subclass of these molecules lacking the DNA-binding domain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.mmi_18030559.x
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  • 10
    Electronic Resource
    Electronic Resource
    Molecular handles on adaptive mutation (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In one experimental system, several handles on the molecular mechanism of apparent adaptive mutation have emerged. The system is reversion of a lac frame-shift mutation in Escherichia coli. The molecular handles include a requirement for homologous recombination; the implication of DNA double-strand breaks as a molecular intermediate; a unique sequence spectrum of −1 deletions in mononucleotide repeats which implies polymerase errors, and also implies a failure of post-synthesis mismatch repair on those errors; and the involvement of sexual functions at some stage of the process. These molecular handles are revealing an unexpected new mechanism of mutagenesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.mmi_18020185.x
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  • 11
    Electronic Resource
    Electronic Resource
    nasST, two genes involved in the induction of the assimilatory nitrite—nitrate reductase operon (nasAB) of Azotobacter vinelandii (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: An operon including two new genes (nasS and nasT) has been defined, cloned and sequenced. The deduced NASS protein is homologous to NRTA from Synechococcus sp. and to NASF from Klebsiella pneumoniae, two proteins involved in nitrate uptake. The predicted NAST polypeptide is homologous to the regulator proteins of the two-component regulatory systems. NASS plays a negative regulatory role in the synthesis of the nitrate and nitrite reductase. NAST is required for the expression of the nitrite—nitrate reductase operon (nasAB). Expression of the nasST operon is not under the control of the NTR system and is not regulated by the nitrogen source. A Φ(nasA—lacZ) fusion has been used to analyse expression of the nasAB operon in three different genetic backgrounds with altered nitrate reductase activity. Beta-galactosidase activity in two of them was independent of nitrate but in a mutant unable to reduce nitrate, nas-4, it was normally induced by nitrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.mmi_18030579.x
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  • 12
    Electronic Resource
    Electronic Resource
    Transcription antitermination: the λ paradigm updated (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Coliphage λ employs systems of transcription termination and antitermination to regulate gene expression. Early gene expression is regulated by the phage-encoded N protein working with a series of Escherichia coli proteins, Nus, at RNA sites, NUT, to modify RNA polymerase to a termination-resistant form. Expression of λ late genes is regulated by the phage-encoded Q antitermination protein. Q, which appears to use only one host factor, acts at a DNA site, qut, to modify RNA polymerase to a termination-resistant form. This review focuses on recent studies which show that: (i) N can mediate antitermination in vitro, independent of Nus proteins, (ii) Early genes in another lambdoid phage HK022 are also regulated by antitermination, where only an RNA signal appears necessary and sufficient to create a termination-resistant RNA polymerase. (iii) A part of the qut signal appears to be read from the non-template DNA strand. (iv) A host-encoded inhibitor of N antitermination appears to act through the NUT site as well as with the α subunit of RNA polymerase, and is antagonized by NusB protein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.mmi_18020191.x
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  • 13
    Electronic Resource
    Electronic Resource
    A role for bacteriophages in the evolution and transfer of bacterial virulence determinants (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A virulence-associated region in the genome of Dichelobacter nodosus has been shown to contain an integrase gene which is highly related to the integrases of Shigella flexneri phage Sf6 and coliphages P4 and φR73, together with open reading frames (vapB, C and D) related to genes borne on plasmids in Neisseria gonorrhoeae, Escherichia coli, Actinobacillus actinomycetemcomitans and Treponema denticola. Similar to P4 and φR73, the vap region is bracketed by putative bacteriophage att sites and is adjacent to a tRNA gene, which suggests that the vap region has been derived by the integration of a bacteriophage, or a plasmid carrying a bacteriophage-related integrase gene. Many similarities in genes and genes clusters encoding virulence determinants have been found in distantly related bacteria. These genes are often located on plasmids in one organism but on the chromosome in others, implying that transmission of the genes has been followed by integration. Thus, the events which have generated the vap regions of D. nodosus may represent a common mechanism for transfer of virulence determinants. A number of genes involved in the virulence of bacterial pathogens are found on integrated bacteriophages, and we suggest that others will prove to be associated with tRNA genes and/or integrase genes derived from bacteriophages. The use of tRNA genes as integration sites for many bacteriophages and plasmids may favour intergeneric transmission, as tRNA genes are highly conserved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.mmi_18020201.x
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  • 14
    Electronic Resource
    Electronic Resource
    ToIC and DsbA are needed for the secretion of STB, a heat-stable enterotoxin of Escherichia coli (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: STB secretion-deficient mutants were isolated using the synthetic transposon TnβIaM. Cultures were plated using a double-membrane system of cellulose acetate and nitrocellulose placed on Luria agar plates containing carbenicillin. The STB bound to the underlying nitrocellulose membrane was detected with anti-STB antibodies. The altered genes of two STB secretion-deficient mutants were identified by conjugation and complementation as toIC and dsbA. In cultures of well-characterized dsbA and toIC mutants, STB was absent from the culture supernatant. The role of ToIC and DsbA in the secretion of peptides is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.mmi_18020237.x
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  • 15
    Electronic Resource
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    Regulation of the heat-shock response depends on divalent metal ions in an hfIB mutant of Escherichia coli (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: HfIB, also called FtsH, is an essential Escherichia coli protein involved in the proteolysis of the heat-shock regulator σ32 and of the phage regulator λcll. The hfIB1(Ts) allele (formerly called ftsH1) conferring temperature-sensitive growth at 42°C is suppressed by loss of the ferric-uptake repressor Fur and by anaerobic growth. We show here that suppression requires TonB-dependent Fe(III) transport in the hfIB1(Ts) fur mutant during aerobic growth at 42°C and Feo-dependent Fe(II) transport during anaerobic growth at 42°C. Temperature-resistant growth of hfIB1(Ts) strains is also observed at 42°C in the presence of a high concentration of Fe(II), Ni(II), Mn(II) or Co(II) salts, but not in the presence of Zn(II), Cd(II), Cu(II), Mg(II), Ca(II) or Cr(III) salts. However, neither Ni(II) nor a fur mutation permits growth in the complete absence of HfIB. The heat-shock response, evaluated by an htpG::lacZ fusion, is overinduced in hfIB1(Ts) strains at 42°C because of stabilization of σ32. Growth in the presence of Ni(II) or in the absence of the Fur repressor abolishes this overinduction in the hfIB1(Ts) strain, and, in the hfIB1(Ts) fur mutant, σ32 is no longer stabilized at 42°C. These results reinforce the recent observation that HfIB is a metalloprotease active against σ32in vitro and suggest that it can associate functionally in vivo with Fe(II), Ni(II), Mn(II) and Co(II) ions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.mmi_18020247.x
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  • 16
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    Regulation of insecticidal crystal protein production in Bacillus thuringiensis (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The production of insecticidal crystal proteins (ICPs) in Bacillus thuringiensis normally coincides with sporulation, resulting in the appearance of parasporal crystalline inclusions within the mother cell. In most instances, the temporal and spatial regulation of ICP gene expression is determined at the transcriptional level by mother-cell-specific sigma factors that share homology with σE and σK from Bacillus subtilis. The crylll ICP genes are a notable exception; these genes are transcribed from σA-like promoters during vegetative growth, are induced or derepressed at the onset of stationary phase, and are overexpressed in sporulation mutants of B. thuringiensis blocked in the phosphorylation of Spo0A, a key regulator of sporulation initiation. Transcription alone, however, cannot account for the impressive ability of this bacterium to accumulate insecticidal proteins. A variety of post-transcriptional and post-translational mechanisms also contribute to the efficient production of ICPs in B. thuringiensis, thus making this bacterium a cost-effective biological control agent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.mmi_18010001.x
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  • 17
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    Genetic organization, nucleotide sequence and regulation of expression of genes encoding phenol hydroxylase and catechol 1,2-dioxygenase in Acinetobacter calcoaceticus NCIB8250 (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We have mutated Acinetobacter calcoaceticus NCIB8250 to growth deficiency on phenol as sole carbon source and isolated genes with similarity to phenol hydroxylase and catechol 1,2-dioxygenase by complementation. Sequence analysis reveals the presence of six open reading frames (ORFs) with similarities to a Pseudomonas multicomponent phenol hydroxylase which are followed by an ORF with similarity to catA from A. calcoaceticus ADP1. Transformation of these genes to ADP1 confers the ability to grow at the expense of phenol as sole carbon source. Primer extension analysis indicates phenol-inducible transcription from an RpoN-dependent promoter sharing sequence similarity with the σ54 consensus promoter sequence, except that the −12 box is GG instead of GC. A catA::lacZ transcriptional fusion shows the same induction profile for β-galactosidase expression as transcription from the σ54-dependent promoter. This result suggests that catA is cotranscribed in the same operon with the phenol hydroxylase-encoding genes and is consistent with the fact that no apparent additional promoter is found for catA by sequence analysis or primer extension. Catechol 1,2-dioxygenase activity is induced in NCIB8250 by benzoate, whereas β-galactosidase expression from the catA::lacZ fusion is not. This observation leads to the hypothesis that two differentially regulated catA genes should be present in that strain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.mmi_18010013.x
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  • 18
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    Identification of the minimal replicon of plasmid pMEA300 of the methylotrophic actinomycete Amycolatopsis methanolica (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The actinomycete Amycolatopsis methanolica contains a 13.3 kb plasmid (pMEA300), capable of enhancing the spontaneous mutation frequency of its host. Depending on the growth medium pMEA300 is not only maintained as an integrated element but can additionally be present as a multicopy, autonomously replicating plasmid. The minimal replicon of pMEA300 was identified. Two unlinked DNA fragments of 2.6 kb and 0.8 kb were required for pMEA300 maintenance. Sequence analysis of the 2.6 kb fragment revealed at least two open reading frames, orfA and orfB, encoding putative proteins of 170 amino acids (18 373 Da) and 416 amino acids (45 260 Da), respectively. No clear similarities were found between the deduced amino acid sequences of the putative orfA and orfB products of pMEA300 and replication proteins identified for various Streptomyces plasmids. The pMEA300 proteins of A. methanolica thus may represent unfamiliar types. The 0.8 kb fragment contained a single complete open reading frame (korA), encoding a protein of 118 amino acids (12 917 Da). The putative KorA protein of pMEA300 shows sequence similarity with various other Streptomyces plasmid-encoded Kor proteins which may belong to the GntR family of transcriptional repressor proteins. The data provide preliminary evidence for the possible involvement of a kil—kor system in autonomous replication of pMEA300.
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    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.mmi_18010021.x
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  • 19
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    Differential expression of two siderophore-dependent iron-acquisition pathways in Erwinia chrysanthemi 3937: characterization of a novel ferrisiderophore permease of the ABC transporter family (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In planta expression of a high-affinity iron-uptake system involving the siderophore chrysobactin in Erwinia chrysanthemi 3937 contributes greatly to invasive growth of this pathogen on its natural host, African violets. A previous study reported that global regulation by iron in this strain was mediated at the transcriptional level via the cbr locus which, when inactivated by insertional mutation, prevents the chrysobactin system from being tightly repressed by FeCl3- Herein, we report the nucleotide sequence of this locus and the functional analysis of its encoded products. Sequence analysis of a 4.8 kb genomic segment of a plasmid encompassing the cbr locus and characterization of the cognate translated products made it possible to uncover a system exhibiting similarity with prokaryotic transporters implicated in the transport of iron complexes. Accordingly, the CbrA product was shown to be the periplasmic component of a permease complex also including two integral membrane proteins, CbrB and CbrC, and the ATP-binding unit CbrD. This system allowed internalization of Fe(III) when supplied to bacterial cells as 59FeCl3 or 59Fe dicitrate, via complexation to a second siderophore recently detected in strain 3937. Most notably, we demonstrate that this second siderophore-mediated iron-acquisition system is operational in bacterial cells grown in the presence of FeCl3. The regulatory effect of cbr was further assessed on a lacZ chrysobactin operon fusion indicating that the transcriptional control exerted by cbr on expression of the chrysobactin system is of homeostatic nature. In conclusion, E. chrysanthemi provides an interesting model in which iron acquisition involves an inductive process resulting in differential expression of two siderophore-mediated pathways in relation to external iron accessibility.
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    Insertion of inverted Ter sites into the terminus region of the Escherichia coli chromosome delays completion of DNA replication and disrupts the cell cycle (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: To investigate the co-ordination between DNA replication and cell division, we have disrupted the DNA replication cycle of Escherichia coli by inserting inverted Ter sites into the terminus region to delay completion of the chromosome. The inverted Ter sites (designated InvTer::spcr) were initially inserted into the chromosome of a Δtus strain to allow unrestrained chromosomal replication. We then introduced a functional tus gene by transforming the InvTer::spcr strain with a plasmid carrying the tus gene under control of an arabinose-inducible promoter. In the presence of 0.2% arabinose, the cells formed long filaments, suggesting that activation of the inverted Ter sites by Tus arrested DNA replication and delayed the onset of cell division. Induction of sfiA, a gene in the SOS regulon, was observed following arrest of DNA replication; however, when a sfiB114 allele was introduced into InvTer::spcr strain, long filaments were still formed, suggesting that the sfi-independent pathway also caused filamentation. Either recA::camr or lexA3 alleles suppressed filamentation when introduced in the InvTer strain. Interestingly, in both the recA::camr and lexA3 mutants, virtually all cells had a nucleoid, suggesting that cell division was proceeding even though DNA replication was not complete. These results suggest that DNA replication and cell division are uncoupled when recA is inactivated or when genes repressed by LexA cannot be induced.
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    Expression of flagella and motility by Shigella (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Since the discovery of Shigella as the aetiologic agent of acute dysentery almost 100 years ago, this organism has been described as a non-motile and non-flagellated organism that invades the human colonic mucosa. In this study, the production of flagella by prototypic strains of all four Shigella species and, moreover, by fresh clinical isolates was demonstrated by electron microscopy. The flagellum of Shigella (flash) is ∼10 µm long and 12–14 nm in diameter and is typically seen emanating from one pole of the bacterium. Flash is composed of a putative structural polypeptide subunit of 33–38 kDa that shares immunological similarities with Escherichia coli, Salmonella spp., and Proteus mirabilis flagellins, and with the recently described recombinant Shigella flagellins (FliCSS and FliCSF) expressed in E. coli K-12. A fliCSS -specific oligo probe hybridized with all four Shigella species, while a fliCSF probe hybridized with all Shigella flexneri and Shigella dysenteriae strains, but not with all Shigella sonnei or Shigella boydii strains, indicating genetic divergence among their flagellin genes. Shigella exhibits motility in low-concentration motility agar under physiological growth conditions. The expression of flash and motility appears to be strictly regulated by unidentified genetic and environmental factors. These heretofore undescribed features may allow the bacteria to circumvent the natural intestinal mucosal defences leading to bacterial colonization and disease. The motility of shigellae may represent an evolutionary adaptation important for bacterial survival.
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    NPI1, an essential yeast gene involved in induced degradation of Gap1 and Fur4 permeases, encodes the Rsp5 ubiquitin—protein ligase (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: When yeast cells growing on a poor nitrogen source are supplied with NH4+ ions, several nitrogen permeases including the general amino acid permease (Gap1p) are rapidly and completely inactivated. This report shows that inactivation by NH4+ of the Gap1 permease is accompanied by its degradation. A functional NPI1 gene product is required for both inactivation and degradation of Gap1p. Molecular analysis of the NPI1 gene showed that it is identical to RSP5. The RSP5 product is a ubiquitin—protein ligase (E3 enzyme) whose physiological function was, however, unknown. Its C-terminal region is very similar to that of other members of the E6-AP-like family of ubiquitin-protein ligases. Its N-terminal region contains a single C2 domain that may be a Ca2+-dependent phospholipid interaction motif, followed by several copies of a recently identified domain called WW(P). The Npi1/Rsp5 protein has a homologue both in humans and in mice, the latter being involved in brain development. Stress-induced degradation of the uracil permease (Fur4p), a process in which ubiquitin is probably involved, was also found to require a functional NPI1/RSP5 product. Chromosomal deletion of NPI1/RSP5 showed that this gene is essential for cell viability. In the viable np1/rsp5 strain, expression of NPI1/RSP5 is reduced as a result of insertion of a Ty1 element in its 5′ region. Our results show that the Npi1/Rsp5 ubiquitin-protein ligase participates in induced degradation of at least two permeases, Gap1p and Fur4p, and probably also other proteins.
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    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.mmi_18010077.x
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    Tissue-specific glycogen branching isoenzymes in a multicellular prokaryote, Streptomyces coelicolor A3(2) (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In the overtly differentiated colonies of Streptomyces coelicolor A3(2), discrete phases of glycogen synthesis are found at the vegetative/aerial mycelium boundary (phase I) and in the immature spore chains at aerial hyphal tips (phase II). We have characterized two S. coelicolor glgB genes encoding glycogen branching enzyme, which are well separated in the genome. Disruption of glgBI led to the formation of abnormal polyglucan deposits at phase I, with phase II remaining normal, whereas disruption of glgBII interfered specifically with phase II deposits, and not with those of phase I. Thus, each branching enzyme isoform is involved in a different phase of glycogen synthesis. This situation contrasts with that in simple bacteria, which typically have a single set of enzymes for glycogen metabolism, and more closely resembles that in plants.
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    Coupling of Escherichia coli hns mRNA levels to DNA synthesis by autoregulation: implications for growth phase control (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The H-NS protein of enteric bacteria is one of the major proteins of the bacterial nucleoid and seems to play an important role in nucleoid structure. Transcription of the hns gene encoding the H-NS protein appears to be negatively regulated by H-NS itself both in vitro and in vivo. We have examined the role of this mode of regulation in wild-type cells in vivo. We find that hns transcription is down-regulated when DNA synthesis is blocked in growing cells, in a manner that is dependent upon continuing H-NS protein synthesis. These data suggest that hns autoregulation serves to match de novo H-NS synthesis to the demands of DNA synthesis and may maintain a relatively constant H-NS:DNA ratio. It has previously been suggested that hns transcription is activated as cells enter stationary phase, which would require a complete relaxation of autoregulatory control given that DNA synthesis decreases at this time. However, we show here that levels of hns mRNA in fact decline at the onset of stationary phase in a manner fully consistent with the autoregulation model. We also fail to detect any significant accumulation of the H-NS protein in stationary phase.
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    Identification of a methyl-accepting chemotaxis protein in Rhodobacter sphaeroides (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Analysis of the DNA sequence directly upstream of the chemotaxis operon of Rhodobacter sphaeroides identified a single gene whose product has strong similarity to the methyl-accepting chemotaxis proteins (MCPs) found in enteric bacteria. The deduced protein had a highly conserved signalling sequence and only one very hydrophobic region at the N-terminus, in contrast to enteric MCPs. A possible cytoplasmic location of the majority of the protein was supported by Western blotting. The mcpA gene was insertionally inactivated and the resulting phenotype examined using swarm plate assays. The mutant lacking McpA lost chemotaxis to a wide range of attractant stimuli but only under aerobic conditions; it retained almost normal chemotaxis under anaerobic/photosynthetic conditions. The identification of a sensory protein which is active only under one set of growth conditions suggests that R. sphaeroides probably has several MCPs, which co-ordinately respond to changes in environmental conditions. Southern hybridization at relaxed stringency to the conserved sequence of the R. sphaeroides and Caulobacter crescentus mcp genes identified three possible additional mcp genes.
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    Cell-surface-bound Yersinia translocate the protein tyrosine phosphatase YopH by a polarized mechanism into the target cell (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: YopH is translocated by cell-surface-bound bacteria through the plasma membrane to the cytosol of the HeLa cell. The transfer mechanism is contact dependent and polarizes the translocation to only occur at the contact zone between the bacterium and the target cell. More than 99% of the PTPase activity is associated with the HeLa cells. In contrast to the wild-type strain, the yopBD mutant cannot deliver YopH to the cytosol. Instead YopH is deposited in localized areas in the proximity of cell-associated bacteria. A yopN mutant secretes 40% of the total amount of YopH to the culture medium, suggesting a critical role of YopN in regulation of the polarized translocation. Evidence for a region in YopH important for its translocation through the plasma membrane of the target cell but not for secretion from the pathogen is provided.
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    Regulatory characteristics and promoter analysis of csiE, a stationary phase-inducible gene under the control of σS and the cAMP—CRP complex in Escherichia coli (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Sigma-S and the cAMP—CRP complex are global regulatory factors involved in stationary-phase induction of large groups of genes in Escherichia coli. csiE, a gene located at 57.25 min (co-ordinate 2674) of the physical map of the E. coli chromosome, is under the control of both of these factors. Sigma-S plays a positive, though not absolutely essential, role in the expression of csiE. Regulation by cAMP—CRP has both positive and negative elements, with the latter being dependent on the presence of σS, whose expression is negatively influenced by cAMP—CRP. csiE has a single transcriptional start site located 33 bp upstream of the initiation codon. By a 5′-deletion approach, we show that 72 bp upstream of the csiE transcriptional start site are sufficient for regulation by σS and cAMP—CRP. A deletion upstream of nucleotide −38 with respect to the start site eliminates positive cAMP—CRP control and makes the remaining expression fully dependent on σS. Our results indicate that transcription at the csiE promoter can be initiated in vivo by σS-containing RNA polymerase alone as well as by σ70-containing RNA polymerase in conjunction with cAMP—CRP or a cAMP—CRP-dependent secondary regulator. The promoter region of poxB, the structural gene for pyruvate oxidase, which is also under the control of σS and cAMP—CRP, is very similar to the corresponding region of csiE, suggesting a similar regulatory mechanism also for poxB.
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    Time-lapsed confocal microscopy reveals temporal and spatial expression of the lysine ɛ-aminotransferase gene in Streptomyces clavuligerus (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: To investigate the temporal and spatial expression patterns of the gene (lat ) encoding lysine ɛ-aminotransferase (LAT) for cephamycin C biosynthesis, a mutant form of green fluorescent protein (mut1GFP) was integrated into the Streptomyces clavuligerus chromosome (strain LH369), resulting in a translational fusion with lat. LAT activity and fluorescence profiles of the recombinant protein paralleled the native LAT enzyme activity profile in wild-type S. clavuligerus, which peaked during exponential growth phase and decreased slowly towards stationary phase. These results indicate that the LAT–Mut1GFP fusion protein retains both LAT and GFP functionality in S. clavuligerus LH369. LH369 produced wild-type levels of cephamycin C in minimal medium culture conditions supplemented with lysine. Time-lapsed confocal microscopy of the S. clavuligerus LH369 strain revealed the temporal and spatial characteristics of lat gene expression and demonstrated that physiological development of S. clavuligerus colonies leading to cephamycin C biosynthesis is limited to the substrate mycelia.
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    An ordered reaction mechanism for bacterial toxin acylation by the specialized acyltransferase HlyC: formation of a ternary complex with acylACP and protoxin substrates (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The 110 kDa haemolysin protoxin (proHlyA) is activated in the Escherichia coli cytosol by acyl carrier protein-dependent fatty acylation of two internal lysine residues, directed by the co-synthesized protein HlyC. Using an in vitro maturation reaction containing purified protoxin peptides and acylACP, we show unambiguously that HlyC possesses an apparently unique acyltransferase activity fully described by Michaelis–Menten analysis. The Vmax of HlyC at saturating levels of both substrates was ≈ 115 nmol acyl group min−1 mg−1 with KmacylACP of 260 nM and KmproHlyA of 27 nM, kinetic parameters sufficient to explain why in vivo HlyC is required at a concentration equimolar to proHlyA. HlyC bound the fatty acyl group from acylACP to generate an acylated HlyC intermediate that was depleted in the presence of proHlyA, but enriched in the presence of proHlyA derivatives lacking acylation target sites. HlyC was also able to bind in vivo 4′-phosphopantetheine. Substitution of conserved amino acids that could act as putative covalent attachment sites did not prevent binding of the fatty acyl or 4′-phosphopantetheine groups. These data and substrate variation analyses suggest that the unique acylation reaction does not involve covalent attachment of fatty acid to the acyltransferase, but rather that it proceeds via a sequential ordered Bi–Bi reaction mechanism, requiring the formation of a non-covalent ternary acylACP–HlyC–proHlyA complex.
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    Identification of dipeptide repeats and a cell wall sorting signal in the fimbriae-associated adhesin, Fap1, of Streptococcus parasanguis (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Fap1, a fimbriae-associated protein, is involved in fimbriae assembly and adhesion of Streptococcus parasanguis FW213 (Wu et al., 1998). In this study, the sequence of the fap1 gene was resolved using a primer island transposition system. Sequence analysis indicated that fap1 was composed of 7659 nucleotides. The predicted Fap1 protein contains an unusually long signal sequence (50 amino acid residues), a cell wall sorting signal and two repeat regions. Repeat regions I and II have a similar dipeptide composition (E/V/I)S, composed of 28 and 1000 repeats respectively. The two regions combined accounted for 80% of the Fap1 coding region. The experimental amino acid composition and isoelectric point (pI) of Fap1 were similar to that predicted from the deduced Fap1 protein. Results of Northern analyses revealed that the fap1 open reading frame (ORF) was transcribed as a 7.8 kb monocistronic message. Insertional inactivation at the 3′ end, downstream of the fap1 ORF, did not affect Fap1, fimbrial expression or bacterial adhesion. Insertional inactivation of fap1 immediately upstream of the repeat region II abolished expression of Fap1 and fimbriae, and was concurrent with a diminution in adhesion of FW213. Inactivation of the cell wall sorting signal of fap1 also eliminated long fimbrial formation and reduced the ability of FW213 to bind to SHA. Fap1 was no longer anchored on the cell surface. Large quantities of truncated Fap1 were found in the growth medium instead. These results suggest that the fap1 ORF alone is sufficient to support Fap1 expression and adhesion, and demonstrate that anchorage of Fap1 on the cell surface is required for long fimbriae formation. These data further document the role of long fimbriae in adhesion of S. parasanguis FW213 to SHA.
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    Analysis of the function of Escherichia coli poly(A) polymerase I in RNA metabolism (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: To help understand the role of polyadenylation in Escherichia coli RNA metabolism, we constructed an IPTG-inducible pcnB [poly(A) polymerase I, PAP I] containing plasmid that permitted us to vary poly(A) levels without affecting cell growth or viability. Increased polyadenylation led to a decrease in the half-life of total pulse-labelled RNA along with decreased half-lives of the rpsO, trxA, lpp and ompA transcripts. In contrast, the transcripts for rne (RNase E) and pnp (polynucleotide phosphorylase, PNPase), enzymes involved in mRNA decay, were stabilized. rnb (RNase II) and rnc (RNase III) transcript levels were unaffected in the presence of increased polyadenylation. Long-term overproduction of PAP I led to slower growth and irreversible cell death. Differential display analysis showed that new RNA species were being polyadenylated after PAP I induction, including the mature 3′-terminus of 23S rRNA, a site that was not tailed in wild-type cells. Quantitative reverse transcriptase–polymerase chain reaction (RT–PCR) demonstrated an almost 20-fold variation in the level of polyadenylation among three different transcripts and that PAP I accounted for between 94% and 98.6% of their poly(A) tails. Cloning and sequencing of cDNAs derived from lpp, 23S and 16S rRNA revealed that, during exponential growth, C and U residues were polymerized into poly(A) tails in a transcript-dependent manner.
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    Quorum sensing in Pseudomonas aeruginosa controls expression of catalase and superoxide dismutase genes and mediates biofilm susceptibility to hydrogen peroxide (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Quorum sensing (QS) governs the production of virulence factors and the architecture and sodium dodecyl sulphate (SDS) resistance of biofilm-grown Pseudomonas aeruginosa. P. aeruginosa QS requires two transcriptional activator proteins known as LasR and RhlR and their cognate autoinducers PAI-1 (N-(3-oxododecanoyl)-l-homoserine lactone) and PAI-2 (N-butyryl-l-homoserine lactone) respectively. This study provides evidence of QS control of genes essential for relieving oxidative stress. Mutants devoid of one or both autoinducers were more sensitive to hydrogen peroxide and phenazine methosulphate, and some PAI mutant strains also demonstrated decreased expression of two superoxide dismutases (SODs), Mn-SOD and Fe-SOD, and the major catalase, KatA. The expression of sodA (encoding Mn-SOD) was particularly dependent on PAI-1, whereas the influence of autoinducers on Fe-SOD and KatA levels was also apparent but not to the degree observed with Mn-SOD. β-Galactosidase reporter fusion results were in agreement with these findings. Also, the addition of both PAIs to suspensions of the PAI-1/2-deficient double mutant partially restored KatA activity, while the addition of PAI-1 only was sufficient for full restoration of Mn-SOD activity. In biofilm studies, catalase activity in wild-type bacteria was significantly reduced relative to planktonic bacteria; catalase activity in the PAI mutants was reduced even further and consistent with relative differences observed between each strain grown planktonically. While wild-type and mutant biofilms contained less catalase activity, they were more resistant to hydrogen peroxide treatment than their respective planktonic counterparts. Also, while catalase was implicated as an important factor in biofilm resistance to hydrogen peroxide insult, other unknown factors seemed potentially important, as PAI mutant biofilm sensitivity appeared not to be incrementally correlated to catalase levels.
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    Residual polyadenylation in poly(A) polymerase I (pcnB ) mutants of Escherichia coli does not result from the activity encoded by the f310 gene (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: As extracts of poly(A) polymerase I (PAP I) deficient strains of Escherichia coli appeared to contain considerable residual polyadenylating activity, efforts were undertaken to identify a second poly(A) polymerase. Recently, a gene (f310 ) encoding the putative second poly(A) polymerase was cloned and sequenced. Here we have tested the ability of the F310 protein to add poly(A) tails in vivo by measuring total poly(A) levels in both f310 mutants and strains that overproduce F310. In addition, we have visualized poly(A) tails and examined ColE1 plasmid copy number in various genetic backgrounds. We also carried out direct biochemical measurements of AMP incorporation, using cell extracts after amplification of F310. All the data obtained indicate that F310 is not a poly(A) polymerase. Although the presence of two potential ATP binding domains in the F310 protein may account for its apparent ATP binding activity, its true biochemical function remains to be identified. In addition, we show that the f310 gene is transcribed, almost exclusively, during stationary phase from a σs promoter.
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    Extensive interplasmidic duplications change the virulence phenotype of the relapsing fever agent Borrelia turicatae (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The relapsing fever agent Borrelia turicatae has two antigenically distinct serotypes, A and B, which differ in their variable small proteins (Vsps) and in their degree of virulence and neurotropism in mice. Each Vsp gene (vspA or vspB) had an expression-linked copy that was unique to the serotype expressing it. This was located on one linear plasmid, which was defined by the upstream sequence. The archived copies of vspA and vspB were each located on different linear plasmids that were the same in both serotypes. In this feature, the mechanism of antigenic variation is similar to that of another relapsing fever agent, B. hermsii. However, in other features, the mechanisms of the two organisms differ. The expressed and archived loci for vspA and vspB of B. turicatae were near the centre of linear plasmids instead of near the telomeres. The vspA and vspB expression loci were duplicate copies of their respective silent loci: from the vsp itself to at least 13–14 kb downstream. Despite the extensive interplasmidic duplications and the internal position of the expression locus, the only detectable difference between serotypes A and B was in whether they expressed VspA or VspB.
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    Ambient pH signal transduction in Aspergillus: completion of gene characterization (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1046/j.1365-2958.1999.01693.x
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    A molecular switch in SecA protein couples ATP hydrolysis to protein translocation (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: SecA, the dimeric ATPase subunit of bacterial protein translocase, catalyses translocation during ATP-driven membrane cycling at SecYEG. We now show that the SecA protomer comprises two structural modules: the ATPase N-domain, containing the nucleotide binding sites NBD1 and NBD2, and the regulatory C-domain. The C-domain binds to the N-domain in each protomer and to the C-domain of another protomer to form SecA dimers. NBD1 is sufficient for single rounds of SecA ATP hydrolysis. Multiple ATP turnovers at NBD1 require both the NBD2 site acting in cis and a conserved C-domain sequence operating in trans. This intramolecular regulator of ATP hydrolysis (IRA) mediates N-/C-domain binding and acts as a molecular switch: it suppresses ATP hydrolysis in cytoplasmic SecA while it releases hydrolysis in SecY-bound SecA during translocation. We propose that the IRA switch couples ATP binding and hydrolysis to SecA membrane insertion/deinsertion and substrate translocation by controlling nucleotide-regulated relative motions between the N-domain and the C-domain. The IRA switch is a novel essential component of the protein translocation catalytic pathway.
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    Expression of the Escherichia coli NRZ nitrate reductase is highly growth phase dependent and is controlled by RpoS, the alternative vegetative sigma factor (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In the absence of oxygen, many bacteria preferentially use nitrate as a terminal electron acceptor for anaerobic respiration. In Escherichia coli, there are two membrane-bound, differentially regulated nitrate reductases. While the physiological basis for this metabolic redundancy is not completely understood, during exponential growth, synthesis of NRA is greatly induced by anaerobiosis plus nitrate, whereas NRZ is expressed at a low level that is not influenced by anaerobiosis or nitrate. In the course of identifying genes controlled by the stationary phase regulatory factor RpoS (σs), we found that the expression of NRZ is induced during entry into stationary phase and highly dependent on this alternative sigma factor. Expression studies, using operon fusions and nitrate reductase assays, revealed that the NRZ operon is controlled mainly at the level of transcription and is induced 10-fold at the onset of stationary phase in rich media. Consistent with previous reports of RpoS expression, the RpoS dependency of NRZ in minimal media was very high (several hundredfold). We also observed a fivefold stationary phase induction of NRZ in an rpoS background, indicating that other regulatory factors, besides RpoS, are probably involved in transcriptional control of NRZ. The RpoS dependence of NRZ expression was confirmed by Northern analyses using RNA extracted from wild-type and rpoS− strains sampled in exponential and stationary phase. In toto, these data indicate that RpoS-mediated regulation of NRZ may be an important physiological adaptation that allows the cell to use nitrate under stress-associated conditions.
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    Flagellar proteins and type III-exported virulence factors are the predominant proteins secreted into the culture media of Salmonella typhimurium (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We analysed all major proteins secreted into culture media from Salmonella typhimurium. Proteins in culture supernatants were collected by trichloroacetic acid precipitation, separated in SDS–polyacrylamide gels and analysed by amino acid sequencing. Wild-type strain SJW1103 cells typically gave rise to nine bands in SDS gels: 89, 67, 58, 52, 50, 42, 40, 35 and (sometimes) 28 kDa. A search of the sequences in the available databases revealed that they were either flagellar proteins or virulence factors. Six of them were flagella specific: FlgK or HAP1 (58 kDa), FliC or flagellin (52 kDa), FliD or HAP2 (50 kDa), FlgE or hook protein (42 kDa), FlgL or HAP3 (35 kDa) and FlgD or hook-cap protein (28 kDa). The other four bands were specific for virulence factors: SipA (89 kDa), SipB (67 kDa), SipC (42 kDa) and InvJ (40 kDa). The 42 kDa band was a mixture of FlgE and SipC. We also analysed secreted proteins from more than 30 flagellar mutants, and they were categorized into four groups according to their band patterns: wild type, mot type, polyhook type and master gene type. Virulence factors were constantly secreted at a higher level in all flagellar mutants except a Δmot (motAB deletion) mutant, in which the amounts were greatly reduced. A new morphological pathway of flagellar biogenesis including protein secretion is presented.
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    The MET3 promoter: a new tool for Candida albicans molecular genetics (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A central technique used to investigate the role of a Candida albicans gene is to study the phenotype of a cell in which both copies of the gene have been deleted. To date, such investigations can only be undertaken if the gene is not essential. We describe the use of the Candida albicans MET3 promoter to express conditionally an essential gene, so that the consequences of depletion of the gene product may be investigated. The effects of environmental conditions on its expression were investigated, using GFP as a reporter gene. The promoter showed an ≈85-fold range of expression, according to the presence or absence of either methionine or cysteine in concentrations in excess of 1 mM. In the presence of either amino acid, expression was reduced to levels that were close to background. We used URA3 as a model to demonstrate that the MET3 promoter could control the expression of an essential gene, provided that a mixture of both methionine and cysteine was used to repress the promoter. We describe an expression vector that may be used to express any gene under the control of the MET3 promoter and a vector that may be used to disrupt a gene and simultaneously place an intact copy under the control of the MET3 promoter. During the course of these experiments, we discovered that directed integration into the RP10 locus gives a high frequency of transformation, providing a means to solve a long-standing problem in this field.
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    Relationships between a new type IV secretion system and the icm/dot virulence system of Legionella pneumophila (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We describe here a Legionella pneumophila type IV secretion system that is distinct from the previously described icm/dot system. This type IV secretion system contains 11 genes (lvh ) homologous to genes of other type IV secretion systems, arranged in a similar manner. The lvh genes were found to be located on a DNA island with a GC content higher than the L. pneumophila chromosome. In contrast to the icm/dot system that was shown to be required for intracellular growth in HL-60-derived human macrophages and Acanthamoeba castellanii, the lvh system was found to be dispensable for intracellular growth in these two hosts. The lvh system was found to be partially required for RSF1010 conjugation, a process that was previously shown to be completely dependent on several icm/dot genes. However, results obtained from analysis of double mutants in the icm/dot genes and the lvh genes revealed that lvh genes can substitute for some components of the icm/dot system for RSF1010 conjugation, but not for intracellular growth. These results indicate that components of the icm/dot system and components of the lvh type IV secretion system are able to interact with one another.
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    Phosphorylation-induced dimerization of the FixJ receiver domain (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The ‘two-component’ transcriptional activator FixJ controls nitrogen fixation in Sinorhizobium meliloti. Phosphorylation of FixJ induces its dimerization, as evidenced by gel permeation chromatography and equilibrium sedimentation analysis. Phosphorylation-induced dimerization is an intrinsic property of the isolated receiver domain FixJN. Accordingly, chemical phosphorylation of both FixJ and FixJN are second-order reactions with respect to protein concentration. However, the second-order phosphorylation constant is 44-fold higher for FixJN than for FixJ. Therefore, the C-terminal transcriptional activator domain FixJC inhibits the chemical phosphorylation of the receiver domain FixJN. Conversely, FixJN has been shown previously to inhibit FixJC activity ≈ 40-fold, reflecting the interaction between FixJN and FixJC. Therefore, we propose that modulation of FixJ activity involves both its dimerization and the disruption of the interface between FixJN and FixJC, resulting in the opening of the protein structure. Alanine scanning mutagenesis of FixJN indicated that the FixJ~P dimerization interface involves Val-91 and Lys-95 in helix α4. Dimerization was required for high-affinity binding to fixK promoter DNA.
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    The phenolic vir gene inducer ferulic acid is O-demethylated by the VirH2 protein of an Agrobacterium tumefaciens Ti plasmid (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Some or possibly all Ti plasmids of Agrobacterium tumefaciens encode a bicistronic operon designated virH, which encodes two proteins, VirH1 and VirH2, that resemble a family of cytochrome P450-type monooxygenases. Expression of this operon is induced by a family of phenolic compounds that induce all other operons within the vir regulon. We hypothesized that either or both of these proteins might metabolize some or all of these phenolic compounds. We therefore tested induction of a vir promoter by a variety of phenolic compounds in isogenic strains that express or lack virH1 and virH2. Although some compounds were equally effective inducers regardless of the virH status, other compounds induced vir expression far more effectively in the virH mutant than in the virH-proficient host. For all tested compounds, VirH2 appeared to be solely responsible for this effect. One such compound, ferulic acid, was chosen for biochemical analysis. Ferulic acid was degraded by a VirH-proficient host but not by a VirH mutant. The wild-type strain released large amounts of a more hydrophilic compound into the cell supernatant. This compound was tested by mass spectroscopy, nuclear magnetic resonance and UV spectroscopy and found to consist of caffeic acid. This indicates that wild-type strains convert virtually all added ferulic acid to caffeic acid, and that VirH2 is essential for this O-demethylation reaction. Ferulic acid was far more toxic than caffeic acid to the wild-type strain, although the wild-type strain was more resistant to ferulic acid than was the virH mutant. Caffeic acid was slowly removed from the broth, suggesting further metabolic reactions.
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    PrfA, the transcriptional activator of virulence genes, is upregulated during interaction of Listeria monocytogenes with mammalian cells and in eukaryotic cell extracts (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Most virulence genes of Listeria monocytogenes are activated by the transcriptional regulator PrfA. Previous studies have shown that environmental parameters, such as temperature, pH, stress conditions and medium composition, affect the expression of PrfA and PrfA-dependent proteins. In this report, we demonstrate a threefold increase in PrfA protein synthesis during infection of mammalian cells, which correlates with the increased activity of the plcA promoter, the major prfA promoter. Increased PrfA synthesis begins when L. monocytogenes adheres to host cells. In addition, we show that the observed induction of PrfA during the interaction of L. monocytogenes with mammalian cells can be reproduced in vitro using total cell extracts. Our data suggest a role for host proteinase K-sensitive protein(s) in PrfA upregulation.
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    Elevated levels of polyamines and trypanothione resulting from overexpression of the ornithine decarboxylase gene in arsenite-resistant Leishmania (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The levels of trypanothione, a glutathione–spermidine conjugate, are increased in the protozoan parasite Leishmania selected for resistance to the heavy metal arsenite. The levels of putrescine and spermidine were increased in resistant mutants. This increase is mediated by overexpression of ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine biosynthesis. Gene overexpression is generally mediated by gene amplification in Leishmania but, here, the mRNA and the enzymatic activity of ODC are increased without gene amplification. This RNA overexpression is stable when cells are grown in the absence of the drug and does not result from gene rearrangements or from an increased rate of RNA synthesis. Transient transfections suggest that mutations in the revertant cells contribute to these elevated levels of RNA. Stable transfection of the ODC gene increases the level of trypanothione, which can contribute to arsenite resistance. In addition to ODC overexpression, the gene for the ABC transporter PGPA is amplified in the mutants. The co-transfection of the ODC and PGPA genes confers resistance in a synergistic fashion in partial revertants, also suggesting that PGPA recognizes metals conjugated to trypanothione.
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    Mutational analysis of the Pseudomonas syringae pv. tomato hrpA gene encoding Hrp pilus subunit (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Plant pathogenic Pseudomonas syringae strains harbour a type III secretion pathway suggested to be involved in the delivery of effector proteins from the bacteria into plant cells. During plant interaction, the bacteria apparently produce surface appendages, termed Hrp pili, that are indispensable for the secretion process. We have created an insertion mutation library, as well as deletion mutations to hrpA, the structural gene encoding Hrp pilin. Analysis of the mutants revealed gene regions important for hrpA expression, pilus assembly and pilus-dependent autoagglutination of the bacteria. The majority of insertions in the amino-terminal half of the pilin were tolerated without bacterial interaction with plants being affected, while the carboxy-terminus appeared to be needed for pilus assembly. Insertions in the 5′ non-translated region and the first codons within the open reading frame affected mRNA production or stability and abolished protein production.
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    A trans-envelope protein complex needed for filamentous phage assembly and export (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Assembly and export of filamentous phage requires four non-capsid proteins: the outer membrane protein, pIV; the inner membrane proteins, pI and pXI; and a cytoplasmic host factor, thioredoxin. Chemical cross-linking of intact cells demonstrates a trans-membrane complex containing pI and pIV. Formation of the complex protects pI from proteolytic cleavage by an endogenous protease. This protection also requires pXI, which is identical to the C-terminal portion of pI. This indicates that pXI, which is required for phage assembly in its own right, is also part of the complex. This complex forms in the absence of any other phage proteins or the DNA substrate; hence, it represents the first preinitiation step of phage morphogenesis. On the basis of protease protection data, we propose that the preinitiation complex is converted to an initiation complex by binding phage DNA, thioredoxin and the initiating minor coat protein(s).
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    Hyperosmotic shock induces the σ32 and σE stress regulons of Escherichia coli (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The rise in the levels of σS that accompanies hyperosmotic shock plays an important role in Escherichia coli survival by increasing the transcription of genes involved in the synthesis and transport of osmoprotectants. To determine if other stress regulons collaborate with σS in dealing with high osmolality, we used single copy fusions of lacZ to representative promoters induced by protein misfolding in the cytoplasm (dnaK and ibp ), extracytoplasmic stress [P3rpoH and htrA(degP )] and cold shock (cspA). Both the σ32-dependent, dnaK and ibp, promoters, and the σE-dependent, P3rpoH and htrA, promoters were rapidly but transiently induced when mid-exponential phase cells were treated with 0.464 M sucrose. The cspA promoter, however, did not respond to the same treatment. Overproduction of the cytoplasmic domain of the σE anti-sigma factor, RseA, reduced the magnitude of osmotic induction in λφ(P3rpoH::lacZ ) lysogens, but had no effect on the activation of the dnaK and ibp promoters. Similarly, induction of the dnaK::lacZ and ibp::lacZ fusions was not altered in either rpoS or ompR genetic backgrounds. Osmotic upshift led to a twofold increase in the enzymatic activity of the λTLF247 rpoH::lacZ translational fusion whether or not the cells were treated with rifampicin, indicating that both heat shock and exposure to high osmolality trigger a transient increase in rpoH translation. Our results suggest that the σ32, σE and σS regulons closely co-operate in the managment of hyperosmotic stress. Induction of the σ32 and σE regulons appears to be an emergency response required to repair protein misfolding and facilitate the proper folding of proteins that are rapidly synthesized following loss of turgor, while providing a mechanism to increase the activity of σS, the primary stress factor in osmoadaptation.
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    Interspecies complementation in Saccharopolyspora erythraea : elucidation of the function of oleP1, oleG1 and oleG2 from the oleandomycin biosynthetic gene cluster of Streptomyces antibioticus and generation of new erythromycin derivatives (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Two glycosyltransferase genes, oleG1 and oleG2, and a putative isomerase gene, oleP1, have previously been identified in the oleandomycin biosynthetic gene cluster of Streptomyces antibioticus. In order to identify which of these two glycosyltransferases encodes the desosaminyltransferase and which the oleandrosyltransferase, interspecies complementation has been carried out, using two mutant strains of Saccharopolyspora erythraea, one strain carrying an internal deletion in the eryCIII (desosaminyltransferase) gene and the other an internal deletion in the eryBV (mycarosyltransferase) gene. Expression of the oleG1 gene in the eryCIII deletion mutant restored the production of erythromycin A (although at a low level), demonstrating that oleG1 encodes the desosaminyltransferase required for the biosynthesis of oleandomycin and indicating that, as in erythromycin biosynthesis, the neutral sugar is transferred before the aminosugar onto the macrocyclic ring. Significantly, when an intact oleG2 gene (presumed to encode the oleandrosyltransferase) was expressed in the eryBV deletion mutant, antibiotic activity was also restored and, in addition to erythromycin A, new bioactive compounds were produced with a good yield. The neutral sugar residue present in these compounds was identified as l-rhamnose attached at position C-3 of an erythronolide B or a 6-deoxyerythronolide B lactone ring, thus indicating a relaxed specificity of the oleandrosyltransferase, OleG2, for both the activated sugar and the macrolactone substrate. The oleP1 gene located immediately upstream of oleG1 was likewise introduced into an eryCII deletion mutant of Sac. erythraea, and production of erythromycin A was again restored, demonstrating that the function of OleP1 is identical to that of EryCII in the biosynthesis of dTDP-d-desosamine, which we have previously proposed to be a dTDP-4-keto-6-deoxy-d-glucose 3,4-isomerase.
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    Conservation of xer site-specific recombination genes in bacteria (1999)
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    Molecular microbiology 34 (1999), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
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    Spontaneous tandem amplification and deletion of the Shiga toxin operon in Shigella dysenteriae 1 (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Only one species of Shigella, Shigella dysenteriae 1, has been demonstrated to produce Shiga toxin (Stx). Stx is closely related to the toxins produced by Shiga toxin-producing Escherichia coli (STEC). In STEC, these toxins are often encoded on lambdoid bacteriophages and are major virulence factors for these organisms. Although the bacteriophage-encoded stx genes of STEC are highly mobile, the stx genes in S. dysenteriae 1 have been believed to be chromosomally encoded and not transmissible. We have located the toxin genes of S. dysenteriae 1 to a region homologous to minute 30 of the E. coli chromosome, within a 22.4 kbp putative composite transposon bracketed by IS600 insertion sequences. This region is present in all the S. dysenteriae 1 strains examined. Tandem amplification occurs via the flanking insertion sequences, leading to increased toxin production. The global regulatory gene, fnr, is located within the stx region, allowing deletions of the toxin genes to be created by anaerobic growth on chlorate-containing medium. Deletions occur by recombination between the flanking IS600 elements. Lambdoid bacteriophage genes are found both upstream and within the region, and we demonstrate the lysogeny of Shigella species with STEC bacteriophages. These observations suggest that S. dysenteriae 1 originally carried a Stx-encoding lambdoid prophage, which became defective due to loss of bacteriophage sequences after IS element insertions and rearrangements. These insertion sequences have subsequently allowed the amplification and deletion of the stx region.
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    Interaction between the F plasmid TraA (F-pilin) and TraQ proteins (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Elaboration of conjugative (F) pili by F+ strains of Escherichia coli requires the activities of over a dozen F-encoded DNA transfer (Tra) proteins. The organization and functions of these proteins are largely unknown. Using the yeast two-hybrid assay, we have begun to analyse binary interactions among the Tra proteins required for F-pilus formation. We focus here on interactions involving F-pilin, the only known F-pilus subunit. Using a library of F tra DNA fragments that contained all the F genes required for F pilus formation in a yeast GAL4 activation domain vector (pACTII), we transformed yeast containing a plasmid (pAS1CYH2traA) encoding a GAL4 DNA-binding domain–F-pilin fusion. Doubly transformed cells were screened for GAL4-dependent gene expression. This screen repeatedly identified only a single Tra protein, TraQ, previously identified as a likely F-pilin chaperone. The F-pilin–TraQ interaction appeared to be specific, as no transcriptional activation was detected in yeast transformants containing pACTIItraQ plasmids and the Salmonella typhi pED208 traA gene cloned in pAS1CYH2. Two traQ segments isolated in the screen against F-pilin were tested for complementation of a traQ null allele in E. coli. One, lacking the first 11 (of 94) TraQ amino acids, restored DNA donor activity, donor-specific bacteriophage sensitivity and membrane F-pilin accumulation to wild-type levels. The second, lacking the first 21 amino acids, was much less effective in these assays. Both TraQ polypeptides accumulated in E. coli as transmembrane proteins. The longer, biologically active segment was fused to the GAL4 DNA-binding domain gene of pAS1CYH2 and used to screen the tra fragment library. The only positives from this screen identified traA segments. The fusion sites between the traA and GAL4 segments identified the hydrophobic, C-terminal domain IV of F-pilin as sufficient for the interaction. As TraQ is the only Tra protein required for the accumulation of inner membrane F-pilin, the interaction probably reflects a specific, chaperone-like function for TraQ in E. coli. Attempts to isolate an F-pilin–TraQ complex from E. coli were unsuccessful, suggesting that the interaction between the two is normally transient, as expected from previous studies of the kinetics of TraA membrane insertion and processing to F-pilin.
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    Histidine kinases: diversity of domain organization (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Histidine kinases play a major role in signal transduction in prokaryotes for the cellular adaptation to environmental conditions and stresses. Recent progress in the three-dimensional structure determination of two representative members of histidine kinases, EnvZ (class I) and CheA (class II), has revealed common structural features, as well as a kinase catalytic motif topologically similar to those of the ATP-binding domains of a few ATPases. They have also disclosed that there are significant differences in domain organization between class I and II histidine kinases, possibly reflecting their distinct locations, functions and regulatory mechanisms. In spite of this diversity, both class I and II histidine kinases use similar four-helix bundle motifs to relay phosphoryl groups from ATP to regulatory domains of response regulators. The previously known so-called transmitter domain of histidine kinase is further dissected into two domains: a CA (Catalytic ATP-binding) domain and a DHp (Dimerization Histidine phosphotransfer) domain for class I, or a CA domain and an HPt (Histidine-containing Phosphotransfer) domain for class II histidine kinases. From a comparative analysis of the CA domains of EnvZ, CheA and their ATPase homologues, the core elements of the CA domain have been derived. The apparent resemblance between DHp and HPt domains is only superficial, and significant differences between them are discussed.
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    Activation of the cycA P2 promoter for the Rhodobacter sphaeroides cytochrome c2 gene by the photosynthesis response regulator (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
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    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The Rhodobacter sphaeroides photosynthesis response regulator, PrrA, positively regulates cycA P2 expression. Deletion analysis has identified sequences within 73 bp upstream of the transcription initiation site that are required for the activation of cycA P2 by PrrA. A mutant form of the Rhodobacter capsulatus PrrA homologue, whose activity is independent of phosphorylation (RegA*), protects an ≈ 26 bp region of cycA P2 that is centred at ≈ −50 from DNase digestion, and activates transcription of a mutant −14T promoter with increased activity when using either R. sphaeroides RNA polymerase or Escherichia coli Eσ70. A 4 bp target site mutation that eliminated DNA binding and transcription activation by RegA*in vitro also abolished PrrA activation of cycA P2 transcription in vivo, indicating that this region contains a PrrA binding site. By analysing the behaviour of the −14T mutant cycA P2 promoter in vivo, we also found that PrrA uses the same target site to activate expression in both the presence and the absence of O2. However, the extent of transcription activation by PrrA at cycA P2 in vivo is greater under anaerobic conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1999.01649.x
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    Testing the ‘+2 rule’ for lipoprotein sorting in the Escherichia coli cell envelope with a new genetic selection (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We report a novel strategy for selecting mutations that mislocalize lipoproteins within the Escherichia coli cell envelope and describe the mutants obtained. A strain carrying a deletion of the chromosomal malE gene, coding for the periplasmic maltose-binding protein (MalE), cannot use maltose unless a wild-type copy of malE is present in trans. Replacement of the natural signal peptide of preMalE by the signal peptide and the first four amino acids of a cytoplasmic membrane-anchored lipoprotein resulted in N-terminal fatty acylation of MalE (lipoMalE) and anchoring to the periplasmic face of the cytoplasmic membrane, where it could still function. When the aspartate at position +2 of this protein was replaced by a serine, lipoMalE was sorted to the outer membrane, where it could not function. Chemical mutagenesis followed by selection for maltose-using mutants resulted in the identification of two classes of mutations. The single class I mutant carried a plasmid-borne mutation that replaced the serine at position +2 by phenylalanine. Systematic substitutions of the amino acid at position +2 revealed that, besides phenylalanine, tryptophan, tyrosine, glycine and proline could all replace classical cytoplasmic membrane lipoprotein sorting signal (aspartate +2). Analysis of known and putative lipoproteins encoded by the E. coli K-12 genome indicated that these amino acids are rarely found at position +2. In the class II mutants, a chromosomal mutation caused small and variable amounts of lipoMalE to remain associated with the cytoplasmic membrane. Similar amounts of another, endogenous outer membrane lipoprotein, NlpD, were also present in the cytoplasmic membrane in these mutants, indicating a minor, general defect in the sorting of outer membrane lipoproteins. Four representative class II mutants analysed were shown not to carry mutations in the lolA or lolB genes, known to be involved in the sorting of lipoproteins to the outer membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1999.01647.x
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    Functional importance of regions in Escherichia coli elongation factor NusA that interact with RNA polymerase, the bacteriophage λ N protein and RNA (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The association of the essential Escherichia coli protein NusA with RNA polymerase increases pausing and the efficiency of termination at intrinsic terminators. NusA is also part of the phage λ N protein-modified antitermination complex that functions to prevent transcriptional termination. We have investigated the structure of NusA using various deletion fragments of NusA in a variety of in vitro assays. Sequence and structural alignments have suggested that NusA has both S1 and KH homology regions that are thought to bind RNA. We show here that the portion of NusA containing the S1 and KH homology regions is important for NusA to enhance both termination and antitermination. There are two RNA polymerase-binding regions in NusA, one in the amino-terminal 137 amino acids and the other in the carboxy-terminal 264 amino acids; only the amino-terminal RNA polymerase-binding region provides a functional contact that enhances termination at an intrinsic terminator or antitermination by N. The carboxy-terminal region of NusA is also required for interaction with N and is important for the formation of an N–NusA–nut site or N–NusA–RNA polymerase–nut site complex; the instability of complexes lacking this carboxy-terminal region of NusA that binds N and RNA polymerase can be compensated for by the presence of the additional E. coli elongation factors, NusB, NusG and ribosomal protein S10.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1999.01618.x
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    Positive co-regulation of the Escherichia coli carnitine pathway cai and fix operons by CRP and the CaiF activator (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Activation of the two divergent Escherichia coli cai and fix operons involved in anaerobic carnitine metabolism is co-dependent on the cyclic AMP receptor protein (CRP) and on CaiF, the specific carnitine-sensitive transcriptional regulator. CaiF was overproduced using a phage T7 system, purified on a heparin column and ran as a 15 kDa protein on SDS–PAGE. DNase I footprinting and interference experiments identified two sites, F1 and F2, with apparently comparable affinities for the binding of CaiF in the cai–fix regulatory region. These sites share a common perfect inverted repeat comprising two 11 bp half-sites separated by 13 bp, and centred at −70 and −127 from the fix transcription start site. They were found to overlap the two low-affinity binding sites, CRP2 and CRP3, determined previously for CRP. Gel shift assays and footprinting experiments suggest that CaiF and CRP bind co-operatively to the F1/CRP2 and F2/CRP3 sites of the intergenic cai–fix region. Moreover, they appeared to serve the simultaneous binding of each other, giving rise to an original multiprotein CRP–CaiF complex enabling RNA polymerase recruitment and local DNA untwisting, at least at the fix promoter. Using random mutagenesis, two CaiF mutants impaired in transcription activation were isolated. The N-terminal A27V mutation affected the structural organization of the activator, whereas the central I62N mutation was suggested to interfere with DNA binding.
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    URL: http://dx.doi.org/10.1046/j.1365-2958.1999.01622.x
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    Tropical Mariculture (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00331.x
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    Effect of processing soybean meal on the apparent digestibility of practical diets for the greenback flounder Rhombosolea tapirina (Günther) (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00367.x
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    Dominance hierarchy formation in Arctic charr Salvelinus alpinus (L.): nutrient digestibility of subordinate and dominant fish (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Arctic charr Salvelinus alpinus (L.) were individually tagged and maintained in circular tanks for 102 days in order to allow the development of dominance hierarchies. At the end of the trial period, the charr were anaesthetized in benzocaine and identified as dominant, beta (β) and subordinate according to a set of established criteria including size, coloration and bite marks. The gut contents were then collected and analysed for apparent digestibility coefficient of nutrients using the chromic oxide method. Subordinate fish had significantly lower specific growth rates and apparent nutrient digestibility coefficients of both dry matter and lipid compared with dominant fish. Although specific growth rate was significantly lower in the β fish compared with dominant charr, this did not influence the apparent digestibility coefficient of nutrients to any major extent.
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    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00374.x
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    The effects of cypermethrin (Excis) and azamethiphos (Salmosan) on lobster Homarus americanus H. Milne Edwards larvae in a laboratory study (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: This research assessed the effects of two chemicals, cypermethrin (Excis) and azamethiphos (Salmosan), used in the treatment of sea lice Lepeophtheirus salmonis (Kroyer) on American lobster Homarus americanus H. Milne Edwards larvae under laboratory conditions. Larvae were exposed to concentrations of 5, 0.5, 0.05, 0.005 and 0 p.p.b. cypermethrin and 100, 10, 1, 0.1 and 0 p.p.b. azamethiphos for durations of 5, 30 and 60 min, 6 and 12 h in artificial seawater. Both treatment chemicals caused significant mortality (P 〈 0.05) of the lobster larvae below the recommended treatment doses of 5 p.p.b. cypermethrin for 1 h and 100 p.p.b. azamethiphos for 1 h. Temperature affected mortality significantly (P 〈 0.05). and interactions between treatment duration and treatment concentration were also significant (P 〈 0.05). LC50 values calculated for the treatment durations ranged from 0.66 to 0.058 p.p.b. at 10 °C and 1.69–0.365 p.p.b. at 12 °C for cypermethrin, and 33.9–1.3 p.p.b. at 10 °C and 50.4–0.9 p.p.b. at 12 °C for azamethiphos treatment, at the above treatment durations. The lowest LC50 values correspond to ≈ 1/90th of the recommended treatment dose for cypermethrin (Excis) at 12 °C and 1/14th at 10 °C; and 1/110th of the recommended treatment dose for azamethiphos (Salmosan) at 12 °C and 1/75th at 10 °C. The research determined variations in observed behavioural treatment effects on lobster larvae exposed to both cypermethrin and azamethiphos (temperature × treatment duration × treatment concentration; cypermethrin P 〈 0.001, azamethiphos P = 0.008). The pattern of effects that occurred at each temperature were, however, similar (cypermethrin P = 0.764; azamethiphos P = 0.218), and ‘intensity of effect’ of the treatment chemicals was positively correlated with an increasing treatment concentration high (r2 = 0.915, r2 = 0.905).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00372.x
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    Maternal and cage effects on genetic parameter estimation for Pacific white shrimp Penaeus vannamei Boone (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Three sets of full-sib families of Pacific white shrimp Penaeus vannamei Boone, produced from females in different reproductive condition (15, 45 and 75 days after ablation and start of production), were used to estimate heritabilities and genetic correlations of growth traits for several larval and grow-out stages of development. Heritabilities for early larval length (nauplii) were larger when estimated from families produced 45 and 75 days after ablation than when estimated from families produced 15 days after ablation, indicating a maternal effect caused by lower reproductive quality of the females used to produce the second and third sets. However, the better reproductive quality of females used to produce the first set resulted in significant density effects on larval length, presumably caused by different mortalities occurring among families during larval culture, which also resulted in an increase in the heritability values estimated for late post-larvae stages. After transfer to grow-out cages in a pond, all estimated heritabilities decreased initially, then increased again. The increase in heritabilities was associated with a negative correlation between growth and density in the cages at 58 days. Lowering densities at this age resulted in a decrease in heritability values at 97 days, but an increase again thereafter. The largest genetic correlation with abdominal weight, the trait of most interest for improvement in shrimp, was total weight. That was followed by cephalothorax weight, width of first abdominal segment, abdominal length and total length. Among these, the trait with a consistently large heritability at 58 and 97 days, and with a large genetic correlation with abdominal weight, was width of first abdominal segment. This trait might provide a secondary or indirect trait to improve abdominal weight when combined with total weight for a selection programme.
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    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00377.x
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    Cultivation of the spotted wolffish Anarhichas minor (Olafsen) – a new candidate for cold-water fish farming (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The spotted wolffish Anarhichas minor (Olafsen), with its rich and tasty fillets, popular skin and high growth rates in captivity, is a promising candidate for cold-water aquaculture. We have established a production line for the wolffish during 5 years of active research on the biology of the species. Our broodstock, sampled from the Barents Sea, has mainly spawned during autumn. The females must be stripped as soon as possible after ovulation. The best egg batches have shown c. 100% fertilization and survival rates between 60% and 80% during the 800- to 960-daydegrees-long incubation period. Rearing temperatures of 6 °C, 8 °C, ambient and decreasing temperatures have turned out to be satisfactory for survival. Treatment with 150 p.p.m. glutardialdehyde twice a month is recommended to control microorganism growth on eggs. Premature hatching has been a problem in individual egg batches; the reasons are not fully understood. Normally hatched individuals are ≈ 22 mm long and well developed, with a small yolk sac, which is completely resorbed after about 4 weeks at 6–8 °C. The fry have been successfully start fed on formulated feed as well as Artemia. Highest early growth rates have been noted at 8 °C, but overall survival was best at 6 °C. On-growth of spotted wolffish juveniles fed formulated dry floating feed at low temperatures in shallow raceways has been promising. After 2, 3 and 4 years, the mean weights of the first generation produced in aquaculture were 0.7, 2.7 and 5.1 kg respectively. These individuals now make up the broodstock at a recently established commercial production facility.
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    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00392.x
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    Hybridization of Mediterranean groupers: Epinephelus marginatus♀×E. aeneus♂ and early development (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00365.x
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    Effects of different feeding regimes on growth, survival and feed conversion of hatchery-reared juveniles of the gastropod mollusc spotted babylon Babylonia areolata (Link 1807) in flowthrough culture systems (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The effects of feeding regimes on the growth, survival and feed conversion of hatchery-reared juvenile spotted babylon Babylonia areolata (Link) were assessed. Six continuous and discontinuous feeding regimes were fed at satiation to triplicate groups of snails in 200-L flowthrough (3.0 L h–1) indoor rectangular tanks for 180 days. Shell length growth rates of juvenile B. areolata did not differ significantly (P 〉 0.05) between the various feeding treatments. Body weight gain and feed conversion of snails were not significantly different between various feeding treatments, nor were there significant differences in mean survival between any of the feeding treatments.
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    Evaluation of juvenile silver perch Bidyanus bidyanus (Mitchell) nutritional needs using high- and low-protein diets at two feeding levels (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Juvenile silver perch Bidyanus bidyanus (Mitchell) of 3.2 g average weight were reared under controlled conditions on diets containing 23.4% and 40.6% protein. Diets were administered at 3% or 6% of the fish biomass per day. Both the protein concentrations and the feeding level of the diet influenced growth and proximate composition of the fish at the end of the 100-day growth trial. The energy requirement for these fish for maintenance was found to be 81.9 kcal × BW–0.8 and, for each unit of energy retained per metabolic body weight, 7.05 needed to be supplied, whereas for each gram of protein retained per metabolic body weight, 5.79 g were required. The results indicate that it is possible to obtain the same weight increment when feeding a 23.4% protein diet at a level of 6% body mass day–1 compared with only 3% body mass day–1 of a 40.6% protein diet. This study provides the first estimation of nutrient requirements for juvenile silver perch, and these estimations require further refinement.
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    The lipostat, hyperphagia and catch-up growth (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The hypothesis that long-term energy intake is matched to energy expenditure arose during the 1950s, and this formed the basis of the lipostatic model for the control of food intake in mammals. This gave rise to an additional hypothesis that body weight varies little over adult life because body fat, a variable related to body mass, is regulated. There is now a large body of evidence that adipose tissue plays a role in the regulation of feeding and body weight in mammals, and the study of the mechanisms by which the brain monitors the signals arising from the adipose tissue is currently a major area of research. After a period of nutritional restriction, a number of compensatory responses are invoked, and these result in hyperphagia, rapid weight increase and the repletion of energy reserves. However, the extent to which animals recover lost body weight has been reported to vary between studies. It is hypothesized that the rate at which animals replete their lipid reserves during catch-up growth may influence the hyperphagic response and, hence, whether or not there is complete recovery of body weight. Preliminary tests carried out using some data collected in studies of catch-up growth in salmonids appear to provide support for the model, but more experimental studies are needed to provide rigorous testing.
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    Diel feeding rhythms of greenback flounder Rhombosolea tapirina (Günther 1862): the role of light–dark cycles and food deprivation (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The role of light–dark (LD) cycles and food deprivation in the regulation of diel feeding rhythms in greenback flounder Rhombosolea tapirina (Günther 1862) was examined. A computerized monitoring system was developed to record uneaten pellets, and food intake was estimated as the difference between pellets presented and those uneaten. Three groups of five fish each (75–281 g) were exposed sequentially to the LD cycles: LD 12:12, LD 12:12 (scotophase advanced by 9 h), LD 6:18, DD, LD 6:6:6:6, LL and LD 12:12 (return to the initial cycle). Illumination was 120 lux at the water surface (complete darkness at scotophase), and water temperature was 15 ± 1 °C. Fish fed mainly during the light hours under LD 12:12 and resynchronized to the scotophase-advanced LD 12:12 regime after about 12 h. Feeding started at the onset of light and extended to the early scotophase under LD 6:18. A circadian feeding rhythm was detected in fish under DD and LD 6:6:6:6 regimes. Under the LL regime, two groups of fish displayed arrhythmic feeding patterns and did not resynchronize to LD 12:12 for at least 13 days. In contrast, the third group of fish exhibited a circadian feeding rhythm under the LL regime and immediately re-entrained to LD 12:12. Fish were deprived of food for a single period of 26–57 h once feeding patterns had been established under LD 12:12, LD 12 : 12 (scotophase advanced by 9 h) and DD regimes, and feed delivery was resumed during the scotophase or subjective night; the timing of feeding rhythms was shifted by the reintroduction of feed, but progressively resynchronized to the LD cycles. The results suggest that the greenback flounder is a diurnal feeder, that a LD 12:12 cycle is a potent environmental cue to entrain circadian feeding rhythms, and that a biological clock is involved in the timing of feeding.
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    Survival and growth of juvenile lobster Homarus gammarus L. raised for stock enhancement within in situ cages (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The growth of juvenile lobster Homarus gammarus L. reared on sandy sediments under laboratory conditions was compared with the growth of lobsters reared within in situ cages in the wild. The caged lobsters, left without any attention or care for 3 months, achieved an average size similar to that attained under optimal laboratory conditions. (8.8 mm carapace length; CL). Growth was positively correlated to cage size and depth. Overall average survival was 66%, ranging from 0% to 90% for clusters of 30 individually caged juveniles.
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    Genotyping of individual fish oocytes based on polymerase chain reaction amplification of mitochondrial DNA (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00347.x
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    Determining sediment properties around a marine cage farm using acoustic ground discrimination: RoxAnnTM (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Sediment traps collected significant quantities of waste solids beneath marine fish cages at a fish farm site in Greece. Diver observation and the absence of dissolved hydrogen sulphide in the water overlying sediments revealed low benthic impacts despite the very low current speeds measured. An acoustic bottom discrimination system, ground-truthed by conventional remote photography, further confirmed the apparently low benthic impact at this site. These results may be explained partly by the large number of fish present around the cages feeding on farm wastes.
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    Survival of amarillo snapper Lutjanus argentiventris (Peters 1869) at different salinities in captivity (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00352.x
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    High allozyme variation and genetic similarity of two populations of commercial penaeids, Penaeus brevirostris (Kingsley) and P. vannamei (Boone), from the Gulf of California (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Genetic resources assessment is considered as the starting point for population management in both fisheries and aquaculture. In this study, we have obtained genetic variability measures of two commercial penaeid shrimp species, Penaeus brevirostris (Kingsley) and P. vannamei (Boone), from the Gulf of California by means of starch electrophoresis analysis of 16 enzymatic systems, plus total protein. Thirty-two loci were resolved, which revealed polymorphism values (P95) of 15.63% in P. brevirostris and 25.00% in P. vannamei. Unbiased expected heterozygosity (He) was 0.076 and 0.105 respectively. These are high genetic variability figures, taking into account the previously low genetic variability, assessed by means of allozyme variation, reported in several penaeid species around the world. Nei’s genetic similarity between the two species is 0.891.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00354.x
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    The effect of transportation on the juvenile scallop Pecten maximus (L.) (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: At the present time, there is little information concerning the effect of transport on the physiology of scallops. Therefore, the overall objective of this study was to use the adenylic energetic charge (AEC) as an indicator of stress in scallops. Three transport trials were carried out: dry transport in polystyrene boxes containing seaweed and transport by vivier lorry at various densities. Post-transport scallop mortality was low for all trials, but the AEC results showed that scallop stress was reduced when animals were transported by vivier truck compared with dry transport. AEC levels in scallops remained high after 24.75 h of vivier transport in trial 2 (0.54–0.69) and after 17 h of vivier transport in trial 3 (0.79–0.82), whereas after 12 h of dry transport in trial 1, AEC levels in the striated muscle had decreased to 0.42. Ammonia concentration increased throughout the trials but did not appear to affect scallop survival in the short term. In general, the results indicate that greater survival can be achieved over longer distances (greater than 17 h) and at higher densities by vivier truck. However, better stability of holding units within tanks and a method to regulate ammonia and pH levels are needed if greater densities are used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00332.x
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    Growth, metamorphosis and feeding behaviour of Rana catesbeiana Shaw 1802 tadpoles at different rearing densities (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: An experiment was carried out to investigate the effects of rearing density on growth, metamorphosis and behavioural patterns of feeding in bullfrog, Rana catesbeiana Shaw, tadpoles. Stage 25 (Gosner) tadpoles from a single cohort were stocked at 0.5, 1.0, 2.0, 4.0 and 8.0 L–1 in 6-L plastic containers. A combination of phytoplankton and supplementary feed was used. There was an inverse relationship between rearing density and growth and metamorphosis above two organisms L–1. Tadpoles reared at 0.5 and 1.0 L–1 reached the metamorphic climax in 135 and 120 days, respectively, whereas more than 80% of all tadpoles reared at 4 and 8 L–1 did not metamorphose at all. Intraspecific competition appeared to be consistent among the cultured organisms regardless of the rearing density. Smaller tadpoles were displaced to sites distant from feeding points during supplementary feed addition, while no displacement was observed during phytoplankton addition. It is concluded that bullfrog tadpoles grow well at up to two organisms L–1 and that intraspecific competition is present within cultured tadpoles regardless of stocking density and may result from intrinsic genetic variability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00335.x
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  • 75
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    Evaluation of AQUI-STM (efficacy and minimum toxic concentration) as a fish anaesthetic/sedative for public aquaculture in the United States (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: A preliminary evaluation of efficacy and minimum toxic concentration of AQUI-STM, a fish anaesthetic/sedative, was determined in two size classes of six species of fish important to US public aquaculture (bluegill, channel catfish, lake trout, rainbow trout, walleye and yellow perch). In addition, efficacy and minimum toxic concentration were determined in juvenile–young adult (fish aged 1 year or older) rainbow trout acclimated to water at 7°C, 12°C and 17°C. Testing concentrations were based on determinations made with range-finding studies for both efficacy and minimum toxic concentration. Most of the tested juvenile–young adult fish species were induced in 3 min or less at a nominal AQUI-STM concentration of 20 mg L–1. In juvenile–young adult fish, the minimum toxic concentration was at least 2.5 times the selected efficacious concentration. Three out of five species of fry–fingerlings (1.25–12.5 cm in length and 〈 1 year old) were induced in ≤ 4.1 min at a nominal concentration of 20 mg L–1 AQUI-STM, with the other two species requiring nominal concentrations of 25 and 35 mg L–1 for similar times of induction. Recovery times were ≤ 7.3 min for all species in the two size classes. In fry–fingerlings, the minimum toxic concentration was at least 1.4 times the selected efficacious concentration. There appeared to be little relationship between size of fish and concentrations or times to induction, recovery times and minimum toxic concentration. The times required for induction and for recovery were increased in rainbow trout as the acclimation temperature was reduced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00339.x
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    Assessment of Pacific oyster, Crassostrea gigas (Thunberg), size and quality using a computer-based shape analysis technique (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00319.x
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    Dominance hierarchies in Arctic charr, Salvelinus alpinus L.: differential cortisol profiles of dominant and subordinate individuals after handling stress (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: We examined the effect of social rank on plasma cortisol dynamics after handling stress in juvenile Arctic charr, Salvelinus alpinus L., reared in groups of 200 individuals in 1.5 m3 circular tanks (rearing density 0.022 kg L–1). Fish obtained by dip-netting were categorized as either socially subordinate, dominant or as holding an intermediate position on the basis of size, skin coloration and occurrence of bite marks. In undisturbed fish, the highest cortisol levels were found in fish ranked as intermediate and the lowest in dominant fish. In contrast to what has been found under conditions of artificial rearing in small groups (two to ten individuals), cortisol was not significantly elevated in subordinates compared with dominant individuals. In small groups of fish, aggressive interactions and restricted access to food may be significant factors leading to increased stress in socially subordinate individuals. Following stress by dip-netting and transfer, the quickest and largest cortisol response was seen in dominant individuals. These results suggest that hypothalamus–pituitary–inter-renal/adrenal axis responsiveness as well as baseline cortisol production is influenced by social rank in fish, as has been shown in other vertebrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00322.x
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    The combined effects of temperature and salinity on embryos and larvae of the black-lip pearl oyster, Pinctada margaritifera (L.) (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: This paper reports on a 4 × 4 factorial design experiment conducted to examine the combined effects of temperature and salinity on embryonic development and growth and survival of black-lip pearl oyster, Pinctada margaritifera (L.) larvae. The temperatures used were 20 °C, 25 °C, 30 °C and 35 °C, and the salinities were 25°/oo, 30°/oo, 35°/oo and 40°/oo. Response surface contour diagrams were generated from the survival and growth data to estimate optimal conditions. Normal development of embryos occurred only from 25 °C to 30 °C. The optimal conditions for maximum survival and growth were 26–29 °C and 28–32°/oo. Temperatures of 35 °C or greater were lethal for larvae and, at all temperatures tested, larval growth and survival were lowest at a salinity of 40°/oo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00324.x
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  • 79
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    Non-specific immunity parameters and the formation of advanced glycosylation end-products (AGE) in rainbow trout, Oncorhynchus mykiss (Walbaum), fed high levels of dietary carbohydrates (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The effects of long-term hyperglycaemia (5 months), through feeding high levels of dietary carbohydrates, on the non-specific immunity parameters of rainbow trout, Oncorhynchus mykiss (Walbaum), was assessed. Fish were fed one of three diets composed of a basal diet containing ≈ 14% digestible carbohydrate which was progressively diluted with gelatinized potato starch in the following ratios of basal diet to supplemental carbohydrate (gelatinized potato starch): 65:00, 65:20, 65:35. The three diets were pair-fed based on the feed intake of the fish fed the diet containing the highest level of starch (65:35) and representing 100% intake. The other diets were then fed at different levels in a manner that allowed all the groups of fish in the same block to receive the same amount of the basal diet [e.g. the basal diet (undiluted, 65:00) was fed at 65% of the dietary intake of the 65:35 diet]. Blood glucose concentrations and relative liver-to-body size increased with increased dietary carbohydrate intake. Feeding supplemental carbohydrates resulted in a small increase in weight gain of the fish at both supplemental levels. Pronephros tissue lysozyme activity and pronephros macrophage superoxide production were not affected by the dietary treatments. The results suggest the presence of advanced glycosylation end-products in muscle tissue collagen, but were not significantly different between treatments. No substantial effect of long-term feeding of a high carbohydrate diet on the non-specific immunity of rainbow trout was observed. However, the results suggest that dietary carbohydrates may have a slight stimulatory effect on phagocytosis at low–moderate levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00330.x
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    Culture of the microalgae Chaetoceros muelleri with Zecer-56, a natural zeolitic product (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Zeolitic products were originally used as biological filters. These products are now used in other biological processes such as the transformation of ammoniun ions present in sea water into nitrite and the decomposition of fish feed. The application of zeolitic products has now been extended to the growth of marine microalgae cultures. The present paper describes the results obtained from cultures of the diatom Chaetoceros muelleri which was grown in artificial sea water in the presence of Zecer-56, a natural zeolitic product. Zecer-56 was found to significantly stimulate the growth of C. muelleri cultures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00310.x
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    Delayed ovarian development and reduced serum steroid levels in female largemouth bass, Micropterus salmoides Lacépède, raised on pelleted feed (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Female largemouth bass, Micropterus salmoides Lacépède, were raised on pelleted feed or a forage diet consisting of goldfish, Carassius auratus (L.). At the start of the present study, forage-fed bass were significantly smaller than pellet-fed bass. Forage-fed bass exhibited a significant increase in body weight, but not length, during the first month of the study; no further increases were seen in subsequent months. Pellet-fed bass did not grow significantly during the course of the study. In forage-fed bass, the gonadosomatic index (GSI) reached maximum levels in March; pellet-fed bass exhibited delayed ovarian recrudescence, reaching peak GSI approximately 4 weeks later than the forage-fed bass. There was no significant difference in the maximum GSI obtained in the two groups of fish. Serum levels of testosterone and oestradiol-17β reflected the pattern of GSI in both groups. Delayed ovarian recrudescence and suppressed serum steroid levels in pellet-fed bass might result from negative feedback effects of elevated levels of steroids found in the pelleted feed. These effects appear to be transient since pellet-fed bass resume ovarian development despite continuing to receive high steroid levels in their feed.
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    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00307.x
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    Culture of the mysid, Mysidopsis almyra (Bowman), (Crustacea: Mysidacea) in a static water system: effects of density and temperature on production, survival and growth (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The effects of animal density and water temperature on the culture of the mysid, Mysidopsis almyra (Bowman), in a static water system were evaluated. An initial set of experiments tested the effects of mysid density on production. Densities of 25, 37.5, 50, 100 and 200 mysids L–1 were placed in trays with 20 L of sea water. Temperatures were maintained at 26 ± 2 °C. A second set of experiments was conducted in the same system at three different temperatures (18 ± 1, 22 ± 1 and 26 ± 2 °C) using a mysid density of 50 mysids L–1 (1000 mysids tray–1). All experiments had a duration of 30 days. The mysids in all trials were cultured at 20 ± 2‰ salinity and fed Artemia nauplii enriched with marine fatty acids. There was a positive correlation between production and mysid densities up to populations of 100 mysids L–1; maximum production was 273 ± 99 hatchlings day–1. At a population density of 200 mysids L–1, high mortality and low production were recorded 4 days after the start of the experiment. The experiments testing different temperatures showed that mysid production was higher at 22 ± 1 °C, although this result was not significant (P 〉 0.05). Growth rates and hatchling survival after 7 days were significantly higher (P 〈 0.05) at 26 ± 2 °C compared to survival and growth at 18 or 22 °C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00309.x
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    Effect of temperature and relative humidity on the tolerance of the Japanese clam, Ruditapes philippinarum (Adams & Reeve), to air exposure (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Laboratory studies showed that higher relative humidity (RH) and lower air temperature increase the tolerance of the Japanese clam, Ruditapes philippinarum (Adams & Reeve), to exposure. Aerial respiration of the clam was also measured. At high RH, the exposure time which gave 50% survival (LT50) was 1.97 and 1.75 times longer than in low RH at air temperatures of 15 and 25 °C, respectively. At 15 °C, all clams previously acclimatized at 15 °C survived for 58 h at low RH and 102 h at high RH. These differences can potentially be exploited to improve the shipment of clams. The aerial respiration experiment showed that the increase of the oxygen consumption rate at 25 °C was greater than that at 15 °C, following an increase in exposure time. The aerial respiration rates of the clams were ≈ 41.6% and 50.0% of those in water at 25 and 15 °C, respectively. The survival of the clams in air was dependent on aerobic rather than anaerobic respiration.
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    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00303.x
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    Astaxanthin deposition in fillets of Atlantic salmon Salmo salar L. fed two dietary levels of astaxanthin in combination with three levels of α-tocopheryl acetate (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The influence of α-tocopheryl acetate (α-TOAc) on plasma concentration and fillet deposition ofdietary astaxanthin was investigated in Atlantic salmon Salmo salar L. The diets were added 30 or 50 mg kg–1 astaxanthin, and 200, 400 or 800 mg kg–1α-TOAc at each astaxanthin level. Improved flesh deposition of astaxanthin by 8–14% was achieved for fish fed diets with 30 and 50 mg kg–1 astaxanthin, respectively, by the dietary addition of 800 compared with 200 mg kg–1α-TOAc. These results were supported by CIE[1976]L*a*b* tristimulus redness measurements (a* value). Plasma astaxanthin concentration mirrored the muscle astaxanthin concentration in the groups of fish fed a diet containing 30 mg kg–1 astaxanthin. The salmon fed a high astaxanthin and low α-TOAc diet had the highest plasma concentration of idoxanthin (P 〈 0.05). Astaxanthin retention was significantly higher (P 〈 0.001) in salmon fed 30 mg kg–1 astaxanthin than in those fed 50 mg kg–1 astaxanthin, but was not significantly affected by dietary α-TOAc. Liver weight, body weight, specific growth rate, feed/gain ratio and mortalities were not affected by dietary α-TOAc levels. In conclusion, the dietary addition of α-TOAc appears to increase astaxanthin fillet deposition in salmonids and may reduce the demand for astaxanthin supplementation. The effect was rather small and requires verification.
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    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00355.x
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    Intranuclear inclusion bodies in the hepatopancreas in cultured penaeoid shrimp Litopenaeus vannamei (Boone) in Ecuador (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00379.x
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    Computer-controlled freezing of rainbow trout Oncorhynchus mykiss (Walbaum) spermatozoa for routine programmes (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The effects of extender composition and freezing rate on cryopreservation efficiency of refrigerated spermatozoa of rainbow trout Oncorhynchus mykiss (Walbaum) were evaluated in order to test the suitability of a computer-controlled ultrafreezer to cryopreserve milt samples obtained in field conditions and stored for several hours. A very highly significant first-order interaction between freezing rate and the type of extender was found. Six of the eight experimental variants did not differ significantly, resulting, after fertilization of eggs with cryopreserved sperm, in a range of 62.3–74.8% of eyed embryos. This procedure was effective for samples stored at 1 °C for 2 days.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00381.x
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    Artificial spawning of carp Cyprinus carpio L.: differences between the effects on reproduction in females of Israeli strain Dor-70 and its cross-breed treated with carp pituitary and Ovopel (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The effects on carp reproduction were investigated in females of the Dor-70 strain and a cross-breed of this line with a Hungarian one of carp pituitary and Ovopel as ovulation stimulators. It was clear that, in the case of the Ovopel treatment, a higher percentage of females spawned, although the weight of eggs obtained was less than that yielded by hypophysed fish, the differences being highly significant (P ≤ 0.01) with respect to the weight in grams and to percentage of female body weight. No statistically significant differences were determined in the quality of eggs, measured by both the fertilization percentage and the percentage of living embryos, obtained after the two stimulators were used. Neither the provenance of females nor the interaction of female provenance and the stimulator has any effect on the traits investigated. The correlation between the percentage of fertilization and the percentage of live embryos was 0.54 for strain Dor-70 and 0.95 for the cross-breed. The multiple regression equations were calculated for strain Dor-70 and for cross-breed 5 separately, where the percentage of living embryos constituted a dependent variable and the mass of a female, mass of eggs in grams and the percentage of fertilization were independent variables. We appraised the regressions as significant for Dor-70 (P ≤ 0.04) and highly significant for the cross-breed (P ≤ 0.0001).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00350.x
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    Genetic changes in Oreochromis shiranus (Trewavas) associated with the early stages of national aquaculture development in Malawi (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: A study was carried out to investigate the genetic diversity during domestication of Oreochromis shiranus (Trewavas) and to see if it could be associated with events in the known history of aquaculture development in Malawi. Five polymorphic microsatellite loci were scored in 14 populations of O. shiranus and one population of O. mossambicus (Peters). The mean number of alleles per locus ranged from 4.4 ± 1.03 to 13.2 ± 3.31 and was higher in the wild populations than in the domesticated populations. Other measures of genetic diversity were also lower in the domesticated compared with the wild populations, and the decline in diversity was correlated with the time elapsed since the founding of the farm stocks. Ordination analysis grouped domesticated populations into three: (1) those that trace their genealogy from Lakes Chiuta and Chilwa populations and are now spread all over the country; (2) those that come from Lakes Malawi and Malombe; and (3) hybrids between O. shiranus and O. mossambicus. Genetic differentiation among farms was strongly influenced by the pattern of known exchanges among the farmers and introgressive hybridization that had occurred between O. shiranus and O. mossambicus in the farmers’ ponds. Thus, the process of genetic changes in the species subsequent to domestication are best explained and predicted by socio-economic factors that influence the behaviour of farmers, rather than by the time-and-distance models of standard population genetics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00364.x
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    Environmental and product quality in finfish aquaculture development: an example from inland Western Australia (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Aquaculture in Western Australian began with the cultivation of trout in the 1930s, although commercial status was not achieved until the cultured pearl industry was established in Broome in the 1950s. Aquaculture, especially in rural Western Australia, remains a relatively new but expanding industry. Aquaculture development in the agricultural areas of Western Australia represents a potential diversification in large tracts of land where salinization has reduced the economic and ecological sustainability of rural industries. The utilization of saline groundwaters for aquaculture presents a major opportunity for economic expansion. The industry is very small and based around finfish species with wide salinity tolerances. The development of an economically and ecologically sustainable industry requires the application of appropriate environmental management procedures, which provide a high-quality product, minimize the impact of the industry on the surrounding environment and provide a long-term competitive advantage.
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    Editorial (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
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    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00357.x
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    Modelling fish food consumption with artificial neural networks (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
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    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00361.x
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    Galanin and β-endorphin as feeding regulators in cyprinids: effect of temperature (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The effects of intracerebroventricular (ICV) and intraperitoneal (IP) administration of galanin and β-endorphin on food intake have been studied in satiated tench held at 21 ± 2 °C. Food intake was evaluated at 0–2 h and 2–8 h after injection. The same treatments were carried out in tench and goldfish acclimated to 10 ± 1 °C. Central administration of either galanin or β-endorphin significantly increased food intake at 2 h and 8 h after injection in tench acclimated to 21 ± 2 °C, but no change in feeding was observed after IP treatments. Low temperature (10 °C) significantly reduced food intake in both tench and goldfish, and neither central nor peripheral administration of galanin or β-endorphin was found to modify feeding. The results indicate that galanin and opioids play a role in the central regulation of feeding in tench, but the stimulatory effect of these neuropeptides did not reverse the feeding inhibition produced by exposure to low temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00360.x
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  • 93
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    Influence of stocking density on growth of juvenile red porgy Pagrus pagrus L. under different feeding conditions (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The influence of stocking density and feeding regime on the growth of red porgy was studied during winter and spring 1997. Fish were held in 500-L tanks at densities of either 50 or 100 fish per tank, and were fed by means of self-feeders under 6 h restricted (day or night) or free-access feeding regimes. Fish were tagged individually, and weight gain was recorded by individual weighing every second week over an 8-week period during each season. In winter, growth was influenced by feeding time. Fish tended to grow best when fed without restriction and worst when fed at night, although differences were not significant when tank means were compared. Stocking density was influential in the spring trial. Fish stocked at low density and feeding freely grew better than high-density fish that fed either freely or at night. The division of fish into three size classes revealed that, within each treatment, no differences occurred among classes, but growth of fish belonging to the same class was influenced by rearing conditions. No significant differences were found among feeding regimes in terms of the coefficients of weight variation ratio (CVf:CVi) and feed efficiency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00363.x
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  • 94
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    Pattern of feed intake in four species of fish under commercial farming conditions: implications for feeding management (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Meal duration and feed ingestion rate were measured in sea cage-reared Atlantic salmon Salmo salar, rainbow trout Oncorhynchus mykiss, yellowtail Seriola quinqueradiata and red sea bream Pagrus major fed dry extruded feed in discrete meals. At the population level, satiation times in yellowtail, salmon and trout were typically about 15–25 min, but time to satiation was longer (60–90 min) in red sea bream. In all species, feed ingestion rate declined progressively during the course of the meal as the fish became satiated. Initial feed ingestion rates in salmon were ≈ 0.3–0.5 kg feed tonne fish–1 min–1 and in trout 0.5–0.9 kg feed tonne fish–1 min–1, although the capacity to deliver feed may have restricted ingestion. Water temperature had little effect on ingestion rates, possibly because the number of meals per day (1–3) was varied with water temperature, and this may have standardized hunger level at the start of meals. Yellowtail ingested feed at ≈ 3.5 kg feed tonne fish–1 min–1 at water temperatures of 18 °C and 28 °C, whereas red sea bream ingested feed at initial rates of 0.6 and 1.4 kg feed tonne fish–1 min–1at 26.5 °C and 18 °C respectively. The findings are discussed in relation to feeding strategies to minimize interfish competition for feed and to improve the ability of fish farmers to detect the point at which fish are satiated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00369.x
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  • 95
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    Diurnal and seasonal variation in feeding patterns of Atlantic salmon, Salmo salar L., in sea cages (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Atlantic salmon, Salmo salar L., in sea cages exhibit feeding patterns that vary both diurnally and seasonally. Hitherto, there are no data reporting feed rate and its variation through a complete annual cycle. Here we present data from Scotland showing diurnal and interseasonal variation in feeding patterns and feeding rates of Atlantic salmon fed daily to satiation from shortly after transfer to seawater until harvest about 11 months later. A major feeding peak regularly occurred soon after dawn, and feeding rates remained high for approximately one hour. Over the remainder of the day, the fish fed at a lower but steady rate. Relative feed intake varied over the trial, being initially high in summer followed by a sharp decline in autumn, and then further declining until fish reached harvest size at the beginning of the following summer. Further investigations of the relationship between variation in circannual feeding patterns and environmental parameters should now be carried out to improve the understanding of the mechanism behind these patterns.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00385.x
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  • 96
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    Periphyton fouling as a marginal energy source in tropical tilapia cage farming (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: In aquaculture, the benefit of autotrophic production within land-based ponds for fish production has long been recognized. In cage culture, organisms growing on the cage net have so far only been considered as a problem. This study investigated the potential production of periphyton on cage nets used in a tropical mixed tilapia culture of Oreochromis mortimeri (Trewavas), Tilapia rendalli (Boulenger) and Oreochromis niloticus (Linnaeus) in Lake Kariba, Zimbabwe. The production of periphyton was assessed experimentally and compared with the energy demand of the caged fish. The tilapias were found to graze intensively on the net, and the primary production of periphyton on the cage net was ≈ 1% relative to the energy demands of the fish.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00344.x
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  • 97
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    Plasmatic levels of cortisol in the response to acute stress in Nile tilapia, Oreochromis niloticus (L.), previously exposed to chronic stress (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Many studies have been made about the physio-logical effects of isolated chronic or acute stress. However, few studies have been made to assess the combination of both responses. The fish submitted to chronic stress may be subjected to an additional acute stressor. The aim of the present work was to evaluate the acute stress response in Nile tilapia Oreochromis niloticus (L.) previously subjected to chronic stress. For this, two experiments were performed. In the first experiment, the fish were subjected to chronic stress followed by an additional acute stress. In the second experiment, the fish were submitted only to an acute stress. The data showed that Nile tilapia fingerlings can adapt to chronic stress situations, and this decreases, but does not eliminate, their capacity to respond to an additional acute stressor. In both experiments, plasma cortisol levels reached a peak 1 h after administration of the acute stressor. In fish previously submitted to chronic stress, the highest concentration of plasma cortisol measured was 196 ng mL–1. This value was significantly different from the cortisol concentration obtained in the second experiment (267 ng mL–1) with non-chronically stressed fish. The data also suggest that the chronic stress response can provoke a reduction in performance and growth rates compared with non-stressed fish.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00348.x
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  • 98
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    Artificial fertilization in turbot, Scophthalmus maximus (L.): different methods and determination of the optimal sperm–egg ratio (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: With the aim of improving artificial fertilization (AF) in turbot, Scophthalmus maximus (L.), a series of fertilization experiments was carried out under dry conditions and different wet conditions (eggs/sea water: 2V/V and V/V). Another series of fertilization experiments was carried out with different quantities of sperm pool to determine the optimal ratio of spermatozoa to eggs for each AF method. Sperm pool from two males and eggs from spawns with a viability rate of 〉 70% were used. The sperm pool’s density (0.4–5.18 × 109 sperm mL–1) and motility (1–5) had been assessed previously. Significantly different fertilization rates were found when comparing 2V/V and V/V wet conditions. Significantly higher fertilization rates were found in dry fertilization when the sperm–egg ratio was 〉 9000 spermatozoa per egg and, under wet condition V/V, at 3000–4000 spermatozoa per egg.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00326.x
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  • 99
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    Settling rate characteristics and nutrient content of the faeces of Atlantic salmon, Salmo salar L., and the implications for modelling of solid waste dispersion (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00334.x
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  • 100
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    The reproductive biology of the amberjack, Seriola dumerilii (Risso 1810). I. Oocyte development in captivity (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: A study of the reproductive biology of the amberjack, Seriola dumerilii, held in captivity was carried out, describing oogenesis as well as the different stages of the ovarian cycle. Seven stages of oocyte development, as well as oogonia, were distinguished. Cortical alveoli were hardly detectable within the oocyte, as they were small, sparse and contained few mucopolysaccharides. It is suggested that their role in the fertilization process might be less important than in other teleost species. Fish aged 3 and 4 years were found to be sexually immature, with ovaries containing only previtellogenic oocytes. Vitellogenesis started in December in fish aged 4 + years. Late-developing ovaries showing deposition of yolk protein granules were found at the end of the 5th year of life (May) in specimens measuring 80.0 ± 3.5 cm standard length. This should be regarded as the minimum size at which sexual maturity is reached in S. dumerilii. Final vitellogenesis and oocyte maturation were, however, inhibited in captivity, and extensive follicular atresia took place as the natural spawning season approached. It is suggested that insufficient gonadotrophic stimulation because of confinement stress may be the cause of failed maturation and spawning in this species under culture conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00336.x
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