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  • 1
    Electronic Resource
    Electronic Resource
    Identification of competence pheromone responsive genes in Streptococcus pneumoniae by use of DNA microarrays (2004)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 51 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Natural genetic transformation in Streptococcus pneumoniae is controlled in part by a quorum-sensing system mediated by a peptide pheromone called competence-stimulating peptide (CSP), which acts to coordinate transient activation of genes required for competence. To characterize the transcriptional response and regulatory events occurring when cells are exposed to competence pheromone, we constructed DNA microarrays and analysed the temporal expression profiles of 1817 among the 2129 unique predicted open reading frames present in the S. pneumoniae TIGR4 genome (84%). After CSP stimulation, responsive genes exhibited four temporally distinct expression profiles: early, late and delayed gene induction, and gene repression. At least eight early genes participate in competence regulation including comX, which encodes an alternative sigma factor. Late genes were dependent on ComX for CSP-induced expression, many playing important roles in transformation. Genes in the delayed class (third temporal wave) appear to be stress related. Genes repressed during the CSP response include ribosomal protein loci and other genes involved in protein synthesis. This study increased the number of identified CSP-responsive genes from approximately 40 to 188. Given the relatively large number of induced genes (6% of the genome), it was of interest to determine which genes provide functions essential to transformation. Many of the induced loci were subjected to gene disruption mutagenesis, allowing us to establish that among 124 CSP-inducible genes, 67 were individually dispensable for transformation, whereas 23 were required for transformation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03907.x
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  • 2
    Electronic Resource
    Electronic Resource
    Aggressiveness of Xanthomonas axonopodis pv. glycines isolates to soybean and hypersensitivity responses by other plants (2005)
    Oxford, UK : Blackwell Science Ltd
    Plant pathology 54 (2005), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Xanthomonas axonopodis pv. glycines (Xag) causes bacterial pustule disease which can significantly reduce the production of soybean. A collection of 26 isolates of Xag from different soybean-production areas of Thailand was shown to differ with regard to aggressiveness on soybean. They also differed in their ability to induce a hypersensitive response (HR) on four cultivars of tobacco and on other plant species including pepper, tomato, cucumber, pea and sesame. Tomato was most sensitive to HR induction by Xag. Isolate KU-P-34017 caused an HR on all the plant species tested. The minimal concentration of KU-P-34017 needed to induce HR on tobacco was approximately 5 × 108 CFU mL−1. A bacterium–plant interaction period of at least 2·5 h was necessary for HR, and different temperatures, relative humidity and light periods did not affect HR development. Inhibitors of eukaryotic metabolism, including cobalt chloride, lanthanum chloride and sodium orthovanadate (completely), and cycloheximide (partially) blocked the HR on tobacco, indicating the association of an active plant response. In contrast, the HR on tomato was inhibited only by cobalt chloride.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3059.2005.01176.x
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  • 3
    Electronic Resource
    Electronic Resource
    Heterothallism in Plasmopara viticola (2001)
    Oxford, UK : Blackwell Science Ltd
    Plant pathology 50 (2001), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Sexuality in the oomycete Plasmopara viticola, the causal agent of grapevine downy mildew, was studied using isolates from five populations from North America and Europe. Leaf discs of Vitis vinifera cv. ‘Chardonnay’ were inoculated with either individual single-sporangiophore isolates, or in all possible pairwise combinations of 25 isolates from New York State, USA. The occurrence of oospores in leaf discs indicated that the pathogen was heterothallic with two mating types, P1 and P2 in a ratio of 11 : 14 for this population. Heterothallism was confirmed when three representative isolates of each mating type from New York were coinoculated with each of 40 isolates from populations of P. viticola from Michigan, Missouri (USA), Germany and Italy. For each isolate tested, oospores formed with either test isolates of P1 or test isolates of P2 mating types, indicating that the isolates were exclusively P1 or P2 only. For these same isolates, no oospores formed as a result of self-crosses. The ratio of P1 : P2 mating types for all isolates in the study was 27 : 38, statistically equivalent to a 1 : 1 ratio according to χ2 analysis (P = 0·68).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.2001.00573.x
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  • 4
    Electronic Resource
    Electronic Resource
    Aeromonas sobria, a causative agent of disease in farmed perch, Perca fluviatilis L. (2005)
    Oxford, UK : Blackwell Science Ltd
    Journal of fish diseases 28 (2005), S. 0 
    Details
    ISSN: 1365-2761
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Significant numbers of perch, Perca fluviatilis, raised on a pilot fish farm in Switzerland presented focal skin lesions on the lateral sides and fin rot. Mortality rates reached levels of up to 1% of the total fish on the farm per day. Virtually pure cultures of Aeromonas sobria were isolated from the liver, kidney, spleen and skin lesions of affected fish. Aeromonas sobria isolated from the farmed perch had a haemolytic effect on sheep and trout erythrocytes, autoaggregated, was cytotoxic for cultured fish cells and possessed genes involved in type III protein secretion. Experimental infection of naïve perch with a single colony isolate of A. sobria from an affected farm fish resulted in the development of clinical signs identical to those seen on the farm. The results indicate that A. sobria can act as a primary pathogen of perch.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2761.2005.00608.x
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  • 5
    Electronic Resource
    Electronic Resource
    A preliminary study on the effects of dietary supplementation of brewers yeast and nucleotides, singularly or in combination, on juvenile red drum (Sciaenops ocellatus) (2005)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 36 (2005), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: This study was designed to evaluate the effects of dietary supplementation with brewers yeast (Brewtech®) and nucleotides (Optimûn), either singularly or in combination, on red drum growth, body composition, stress responses and possible resistance to Amyloodinium ocellatum infection. Juvenile red drum (∼1 g initially) fed practical fish-meal-based diets for 6 weeks had similar weight gain regardless of whether the diet was unsupplemented (basal) or supplemented with brewers yeast (2% of diet), nucleotides (Optimûn at 0.2% of diet) or both brewers yeast (2% of diet) and nucleotides (Optimûn at 0.2% of diet). Dietary effects on hepatosomatic index, intraperitoneal fat ratio or whole-body composition were not significant, except that fish fed the singular nucleotide supplement had a significantly higher whole-body lipid content compared with fish fed the basal diet. No significant dietary effects on cortisol response were observed after a 15 min confinement stress test perhaps because of the extreme variation among individual fish. Subsequently, in situ challenge by co-habitation with A. ocellatum caused 100% mortality regardless of dietary treatment within a 48 h period. It is concluded that dietary supplementation of brewers yeast and nucleotides did not promote enhanced growth or improved cortisol response and resistance to uncontrolled amyloodiniosis in juvenile red drum, at least at the tested dosages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2109.2005.01333.x
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  • 6
    Electronic Resource
    Electronic Resource
    A phase-variable capsule is involved in virulence of Campylobacter jejuni 81-176 (2001)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 40 (2001), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Campylobacter jejuni strain 81-176 (HS36, 23) synthesizes two distinct glycan structures, as visualized by immunoblotting of proteinase K-digested whole-cell preparations. A site-specific insertional mutant in the kpsM gene results in loss of expression of a high-molecular-weight (HMW) glycan (apparent Mr 26 kDa to 〉 85 kDa) and increased resolution of a second ladder-like glycan (apparent Mr 26–50 kDa). The kpsM mutant of 81-176 is no longer typeable in either HS23 or HS36 antisera, indicating that the HMW glycan structure is the serodeterminant of HS23 and HS36. Both the kpsM-dependent HMW glycan and the kpsM-independent ladder-like structure appear to be capsular in nature, as both are attached to phospholipid rather than lipid A. Additionally, the 81-176 kpsM gene can complement a deletion in Escherichia coli kpsM, allowing the expression of an α2,8 polysialic acid capsule in E. coli. Loss of the HMW glycan in 81-176 kpsM also increases the surface hydrophobicity and serum sensitivity of the bacterium. The kpsM mutant is also significantly reduced in invasion of INT407 cells and reduced in virulence in a ferret diarrhoeal disease model. The expression of the kpsM-dependent capsule undergoes phase variation at a high frequency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2001.02431.x
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  • 7
    Electronic Resource
    Electronic Resource
    Identification and characterization of genes required for post-translational modification of Campylobacter coli VC167 flagellin (1996)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 19 (1996), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Two genes have been identified in Campylobacter coli VC167 which are required for the biosynthesis of post-translational modifications on flagellin proteins. The ptmA gene encodes a protein of predicted Mr 28 486 which shows significant homology to a family of alcohol dehydrogenases from a variety of bacteria. The ptmB gene encodes a protein of predicted Mr 26 598 with significant homology to CMP-N-acetylneuraminic acid synthetase enyzmes involved in sialic acid capsular biosynthesis in Neisseria meninigitidis and Escherichia coli K1. Site-specific mutation of either ptmA or ptmB caused loss of reactivity with antisera specific to the post-translational modifications and a change in the isoelectric focusing fingerprints relative to the parent strains. Mutation of ptmB, but not of ptmA, caused a change in apparent Mr of the flagellin subunit in SDS–PAGE gels. The ptmA and ptmB genes are present in other strains of Campylobacter. In a rabbit model the ptmA mutant showed a reduced ability to elicit protection against subsequent challenge with heterologous strains of the same Lior serotype compared to the parental wild-type strain. This suggests that the surface-exposed post-translational modifications may play a significant role in the protective immune response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1996.369895.x
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  • 8
    Electronic Resource
    Electronic Resource
    CheY-mediated modulation of Campylobacter jejuni virulence (1997)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 23 (1997), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Four motile, non-adherent and non-invasive mutants of Campylobacter jejuni 81-176 generated by a site-specific insertional mutagenesis scheme were characterized at the molecular level and all contained a duplication of the same region of the chromosome. When this region was cloned from wild-type 81-176 and transferred into 81-176 on a shuttle plasmid, the same non-invasive phenotype as the original mutants was observed, suggesting that the region contained a repressor of adherence and invasion. The smallest piece of DNA identified which was capable of repressing adherence and invasion was a 0.8 kb fragment encoding the cheY gene of C. jejuni. To confirm further that CheY was responsible for the observed non-adherent and non-invasive phenotypes, the cheY gene was inserted into the arylsulfatase gene of 81-176 to generate a strain with two chromosomal copies of cheY. This diploid strain displayed the same non-adherent and non-invasive phenotype as the original mutants. Insertional inactivation of the cheY gene in 81-176 resulted in an approx. threefold increase in adherence and invasion in vitro, but this strain was unable to colonize or cause disease in animals. The diploid cheY strain, although able to colonize mice, was attenuated in a ferret disease model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1997.2861650.x
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