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  • 1
    Series available for loan
    Series available for loan
    Würzburg : Inst. für Geographie der Univ.
    Associated volumes
    Call number: ZS-270(95)
    In: Würzburger geographische Arbeiten
    Type of Medium: Series available for loan
    Pages: XIII, 350 S.
    Series Statement: Würzburger geographische Arbeiten 95
    Classification:
    D. 4.
    Language: German
    Note: Zugl.: Würzburg, Univ., Diss., 1968
    Location: Lower compact magazine
    Branch Library: GFZ Library
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  • 2
    ISSN: 1432-072X
    Keywords: Bradyrhizobium japonicum ; Electron transfer flavoprotein ; etf Genes ; fix Genes ; Nitrogen fixation ; Phylogenetic tree ; Protein family
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A group of four co-regulated genes (fixA, fixB, fixC, fixX) essential for symbiotic nitrogen fixation has been described in several rhizobial species, includingBradyrhizobium japonicum. The complete nucleotide sequence of theB. japonicum fixA, fixB andfixC, genes is reported here. The derived amino acid sequences confirmed the previously noted sequence similarity between FixA and the β-subunit and between FixB and the α-subunit of mammalian andParacoccus denitrificans electron transfer flavoproteins (ETF). Since the classical role of ETF is in β-oxidation of fatty acids, a process unrelated to nitrogen fixation, we rationalized thatB. japonicum ought to contain bona fideetf genes in addition to theetf-like genesfixA andfixB. Therefore, we identified, cloned, sequenced, and transcriptionally analyzed theB. japonicum etfSL genes encoding the β-and α-subunits of ETF. TheetfSL genes, but not thefix genes, are transcribed in aerobically grown cells. An amino acid sequence comparison between all available ETFs and ETF-like proteins revealed the existence of two distinguishable subfamilies. Group I comprises housekeeping ETFs that link acyl-CoA dehydrogenase reactions with the respiratory chain, such as in the fatty acid degradation pathway.B. japonicum EtfS and EtfL clearly belong to this group. Group II contains ETF-like proteins that are synthesized only under certain specific growth conditions and receive electrons from the oxidation of specific substrates. The products of the anaerobically inducedfixA andfixB genes ofB. japonicum are members of that group.B. japonicum is the first example of an organism in which genes for proteins of both groups I and II of the ETF family have been identified.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-072X
    Keywords: Key wordsBradyrhizobium japonicum ; Electron ; transfer flavoprotein ; etf Genes ; fix Genes ; Nitrogen ; fixation ; Phylogenetic tree ; Protein family
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A group of four co-regulated genes (fixA, fixB, fixC, fixX) essential for symbiotic nitrogen fixation has been described in several rhizobial species, including Bradyrhizobium japonicum. The complete nucleotide sequence of the B. japonicum fixA, fixB and fixC, genes is reported here. The derived amino acid sequences confirmed the previously noted sequence similarity between FixA and the β-subunit and between FixB and the α-subunit of mammalian and Paracoccus denitrificans electron transfer flavoproteins (ETF). Since the classical role of ETF is in β-oxidation of fatty acids, a process unrelated to nitrogen fixation, we rationalized that B. japonicum ought to contain bona fide etf genes in addition to the etf-like genes fixA and fixB. Therefore, we identified, cloned, sequenced, and transcriptionally analyzed the B. japonicum etfSL genes encoding the β- and α-subunits of ETF. The etfSL genes, but not the fix genes, are transcribed in aerobically grown cells. An amino acid sequence comparison between all available ETFs and ETF-like proteins revealed the existence of two distinguishable subfamilies. Group I comprises housekeeping ETFs that link acyl-CoA dehydrogenase reactions with the respiratory chain, such as in the fatty acid degradation pathway. B. japonicum EtfS and EtfL clearly belong to this group. Group II contains ETF-like proteins that are synthesized only under certain specific growth conditions and receive electrons from the oxidation of specific substrates. The products of the anaerobically induced fixA and fixB genes of B. japonicum are members of that group. B. japonicum is the first example of an organism in which genes for proteins of both groups I and II of the ETF family have been identified.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 141 (1985), S. 260-265 
    ISSN: 1432-072X
    Keywords: (3H) Tetracycline purification ; Initial uptake kinetics ; Monophasic tetracycline uptake ; Tetracycline binding ; Temperature effect on tetracycline uptake ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Experiments measuring the initial uptake of commercial (3H) tetracycline exhibit two distinct kinetic phases: a rapid phase followed by a slow phase. (3H) tetracycline purified by chromatography on a Dowex 50WX2 column exhibited only monophasic rapid uptake when tested with susceptible Escherichia coli cells. Cyanide inhibited the uptake of purified (3H) tetracycline only partially while transport of proline and maltose was entirely abolished. Energy independent accumulation of tetracycline may be accounted for by binding to cellular constituents. Uptake of tetracycline-as measured by inhibition of β-galactosidase synthesis-was strongly affected by a shift in temperature from 37°C to 21°C while carrier-mediated transport systems revealed only minor reductions. Taken together with the non-saturability of tetracycline uptake and the evidence for diffusion of tetracycline through phospholipid bilayers [Argast and Beck (1984) Antimicrob Agents Chemother 26:263–265] these data support the hypothesis that tetracycline enters the cytoplasm by diffusion.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-072X
    Keywords: Chlamydomonas reinhardtii ; Gametic differentiation ; Light requirement ; Light-pulse-studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Gametes of Chlamydomonas reinhardtii synthesize numerous proteins not observed in vegetative cells and vice versa. Gametogenesis induced changes in gene expression were confirmed by SDS-PAGE of in vitro translation products using total RNA from gametes and vegetative cells. Vegetative cells and gametes thus represent two cell types with distinct patterns of gene expression. The generation of mature gametes from liquid cultures of asynchronously growing vegetative cells was dependent on light. This light requirement could not be substituted for by an organic source of energy and carbon, indicating that light serves as a signal in gametogenesis. The light signal was shown to become effective only after preincubation in nitrogen-free medium. This delayed competence for light indicates that the two external signals — nitrogen-starvation and light —may function in sequence. Execution of the light dependent step in gamete formation required cytoplasmic protein synthesis and RNA synthesis.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science, Ltd
    Physiologia plantarum 115 (2002), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In the search for a Chlamydomonas reinhardtii photoreceptor that may mediate blue-light-induced responses we identified a gene that encodes a protein with a structure typical for that of members of the phototropin family, i.e. two LOV domains that may function in flavin mononucleotide binding and a ser/thr kinase domain. The amino acid sequences of these domains are closely related to those of higher plant phototropins. This single-copy gene (Phot) encodes a protein with a calculated molecular mass of 81.4 kDa which is distinctly smaller than the homologous proteins of higher plants that exhibit molecular masses around 120 kDa. Expression analyses revealed rather constant levels of Phot mRNA and Phot protein in vegetative cells incubated in the dark and in cells undergoing gametogenesis. Only vegetative cells in the light showed a reduced expression of the Phot gene. Cell fractionation studies revealed that the protein is membrane-associated. In higher plants, phototropins were shown to be bound to the plasma membrane. However, the expression of a Phot-GFP gene fusion in tobacco protoplasts revealed an association of the fusion protein with the endogenous membrane network of the cell.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 83 (1991), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In the sexual life cycle of Chlamydomonas reinhardtii, three types of cells can be distinguished: vegetative cells, gametes, and zygotes. Using is vivo pulse labelling of proteins with 35S-sulfate, followed by two-dimensional separation of the polypeptides on polyacrylamide gels, we analyzed the patterns of protein synthesis typical for each cell type. Approximately 20% of the proteins detected were synthesized at very different rates when the pattern from vegetative cells was compared to that of gametes or zygotes. Gamete formation from vegetative cells is a two-step process controlled by two extrinsic signals: first, nitrogen-starvation induces the differentiation of vegetative cells to pregaroetes, which are then competent for a light–induced differentiation to mature gametes. The majority of the changes in rate of synthesis of different proteins during the switch from vegetative cells to gametes was observed already in pregametes. Between the stages of pregametes and gametes, changes in the rates of synthesis of four proteins were detected. Induction of zygote germination resulted in complex changes in the patterns of gene expression. Evidence is presented for three groups of proteins whose synthesis is turned on or turned off during zygote germination.
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  • 8
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The genes for a new type of a haem-copper cytochrome oxidase were cloned from Rhodobacter capsulatus strain 37b4, using the Bradyrhizobium japonicum fixNOQP gene region as a hybridizing probe. Four genes, probably organized in an operon (ccoNOQP), were identified; their products share extensive amino acid sequence similarity with the FixN, O, Q and P proteins that have recently been shown to be the subunits of a cb-type oxidase. CcoN is a c-type cytochrome, CcoO and CcoP are membrane-bound mono- and dihaem c-type cytochromes and CcoQ is a small membrane protein of unknown function. Genes for a similar oxidase are also present in other non-rhizobial bacterial species such as Azoto-bacter vinelandii, Agrobacterium tumefaciens and Pseudomonas aeruginosa, as revealed by polymerase chain reaction analysis. A ccoN mutant was constructed whose phenotype, in combination with the structural information on the gene products, provides evidence that the CcoNOQP oxidase is a cytochrome c oxidase of the cb type, which supports aerobic respiration in R. capsulatus and which is probably identical to the cbb3-type oxidase that was recently purified from a different strain of the same species. Mutant analysis also showed that this oxidase has no influence on photosynthetic growth and nitrogen-fixation activity.
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  • 9
    ISSN: 1432-0983
    Keywords: rRNA promoters ; Maize chloroplasts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Restriction fragments containing upstream sequences of the rRNA operon from Zea mays chloroplasts were tested for promoter activity in vivo by insertion into an E. coli promoter-probe vector. The expression of this vector's reporter gene, which codes for alkaline phosphatase, was stimulated more than 1,500-fold upon linkage with the chloroplast rRNA promoter. Site specific mutagenesis of the invariant T of the −10 sequence of this promoter reduced the expression of the reporter gene to 2% of the wild type. This indicates that the chloroplast rRNA promoter, which directs transcriptional initiation 117 by upstream of the 16S rRNA gene, is also active in the bacterial system. A restriction fragment further upstream containing the gene for tRNAVal (GAC) also showed strong promoter activity (29% as compared with the rRNA promoter). This promoter activity probably reflects the chloroplast promoter directing the synthesis of the tRNAVal (GAC) primary transcript. Surprisingly, this restriction fragment also displayed promoter activity (13% compared with the rRNA promoter) in reverse orientation.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-2048
    Keywords: Key words: Chlamydomonas ; Gametogenesis ; Nitrate reductase mutants ; Nitrate signal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract.  The effect of nitrate on gamete differentiation as well as on the expression of genes involved in gametogenesis, nitrogen scavenging, and nitrate assimilation has been analyzed in wild-type and mutant strains of Chlamydomonas reinhardtii. Nitrate prevented gamete formation from wild-type strains and caused a strong reduction in the number of zygotes recovered in genetic crosses between nitrate-assimilation-deficient mutants, thus suggesting that nitrate by itself is providing a negative regulatory signal for the sexual differentiation of the alga. Addition of nitrate at low concentrations to wild-type cells, after an initial period of nitrogen starvation, resulted in a drastic decrease in transcript levels of both nitrate-assimilation genes (NIA1 and NRT2;1) and genes induced after N-starvation (NCG2 and NCG4). This strong effect of nitrate was due to its assimilation products since it was not evident in nitrate-assimilation mutants. A slight negative effect of nitrate on NCG4 expression was only observed in the mutant. Nitrate by itself was also found to provide a negative signal for the expression of gamete-specific genes (GAS3 and GAS18) in mutants incapable of assimilating nitrate.
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