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  • 1
    Electronic Resource
    Electronic Resource
    Two differentially regulated nitrate reductases required for nitrate-dependent, microaerobic growth of Bradyrhizobium japonicum (1994)
    Springer
    Archives of microbiology 162 (1994), S. 310-315 
    Details
    ISSN: 1432-072X
    Keywords: Bradyrhizobium japonicum ; Nitrate ; Membrane-bound nitrate reductase ; Nitrate reductase mutants ; Microaerobiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Native PAGE of Triton x-100-solubilized membranes from Bradyrhizobium japonicum strain PJ17 grown microaerobically (2% O2, v/v) in defined nitrate-containing medium resolved two catalytically active nitrate reductase (NR) species with apparent molecular masses of 160 kDa (NRI) and 200 kDa (NRII). NRI and NRII were also found in membranes from cells of strain PJ17 that were first grown in defined medium with glutamate and further incubated microaerobically in the presence of 5 mmol/l KNO3. However, only NRI was detected in cell membranes of strain PJ17 when nitrate was omitted from the microaerobic incubation medium. Four mutants unable to grow at low O2 tension in the presence of nitrate were isolated after transposon Tn5 mutagenesis. Membranes from mutants GRF110 and GRF116 showed mainly NRI, while the other two mutants, GRF3 and GRF4, expressed mostly NRII. These results indicate that the ability of B. japonicum PJ17 to grow under microaerobic conditions depends upon the presence of two membrane-bound NR enzymes whose synthesis seem to be independently induced by microaerobiosis (NRI) or by both microaerobiosis and nitrate (NRII).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00263777
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  • 2
    Electronic Resource
    Electronic Resource
    Changes in the glycosylation pattern at the reducing end of azorhizobial Nod factors affect nodulation efficiency (1998)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 158 (1998), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The Nod factors of Azorhizobium caulinodans ORS571 are lipo-chitooligosaccharides that at the reducing end can be unsubstituted, substituted with a l-fucosyl group, with a d-arabinose, or with both groups at the same time. These lipo-chitooligosaccharides are the compounds produced by the bacteria during the signal exchange with their host plant at the onset of the nodulation process. By the use of wild-type and mutant strains, the role of the different Nod factor glycosylations on the nodulation behavior was checked. The mere presence of the d-arabinosyl group at the reducing end of the lipo-chitooligosaccharides resulted in a higher number of nodules on roots of Sesbania rostrata, whereas the presence or absence of l-fucose had no effect. The situation is the opposite in other tropical legumes that respond to A. caulinodans ORS571: the l-fucose is the major determinant of nodulation, whereas the presence of d-arabinose is less significant. By the use of a β-glucuronidase reporter fusion, A. caulinodans ORS571 was shown to colonize nodules or nodule-like tissues induced on cowpea and bean, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1998.tb12826.x
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  • 3
    Electronic Resource
    Electronic Resource
    Role of nodl and nodj in lipo-chitooligosaccharide secretion in Azorhizobium caulinodans and Escherichia coli (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 20 (1996), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Lipo-chitooligosaccharide (LCO) Nod factors are produced and secreted by rhizobia and trigger nodule development in leguminous host plants. The products of the bacterial nodlJ genes are related to transporters of capsular polysaccharides and were proposed to be involved in LCO transport. We have studied nodlJ of Azorhizobium caulinodans ORS571 by analysis of cell-associated and secreted radioactively labelled Nod factors in wild-type ORS571, a nodJ mutant and a complemented strain. Secretion was strongly reduced in the nodJ mutant, and restored to wild-type levels after complementation. Constructs were made for expression of combinations of different nod genes in Escherichia coli DH5a. The strain DH5α(pUCNABCSU) synthesized LCOs, but they were only secreted when a plasmid containing both nodl and nodJ was supplied in trans, nodi or nodJ alone was not sufficient. In E. coli as well as in Azorhizobium, the nod/J-encoded transporter showed a specificity for more hydrophilic LCOs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1996.tb02540.x
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  • 4
    Electronic Resource
    Electronic Resource
    Fucosylation and arabinosylation of Nod factors in Azorhizobium caulinodans: involvement of nolKnodZ as well as noeC and/or downstream genes (1996)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 21 (1996), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The DNA region downstream of the nodABCSUIJ operon of Azorhizobium caulinodans was further characterized and two new genes, nodZ and noeC were identified in the same operon. The A. caulinodans wild-type strain produces a population of Nod factors that, at the reducing end, are either unmodified or carry a D-arabinosyl and/or an L-fucosyl branch. Nod factors produced by Tn5-insertion mutants in nodZnoeC, and the separate nolK locus, were analysed by thin-layer chromatography and mass spectrometry. Fucosylation of Nod factors depended on both nodZ and nolK. Arabinosylation depended on noeC and/or downstream genes. Protein extracts of A. caulinodans contained an enzymatic activity for fucose transfer from GDP-fucose to chitooligosaccharides and to Nod factors. By mutant analysis and expression of nodZ in Escherichia coli, the fucosyltransferase activity was ascribed to the protein encoded by nodZ. In addition, a Nod factor fucosyltransferase activity, independent of nodZ or other known nod genes, was detected in A. caulinodans. Finally, on the basis of sequence similarity of the nolK gene product, and mass spectrometric analysis of Nod factors produced by a nolK mutant, we propose that this gene is involved in the synthesis of GDP-fucose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1996.6451366.x
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