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  • 1
    Electronic Resource
    Electronic Resource
    Solute-binding protein-dependent ABC transporters are responsible for solute efflux in addition to solute uptake (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: The ATP-binding cassette (ABC) transporter superfamily is one of the most widespread of all gene families and currently has in excess of 1100 members in organisms ranging from the Archaea to man. The movement of the diverse solutes of ABC transporters has been accepted as being strictly unidirectional, with recent models indicating that they are irreversible. However, contrary to this paradigm, we show that three solute-binding protein-dependent (SBP) ABC transporters of amino acids, i.e. the general amino acid permease (Aap) and the branched-chain amino acid permease (Bra) of Rhizobium leguminosarum and the histidine permease (His) of Salmonella typhimurium, are bidirectional, being responsible for efflux in addition to the uptake of solutes. The net solute movement measured for an ABC transporter depends on the rates of uptake and efflux, which are independent; a plateau is reached when both are saturated. SBP ABC transporters promote active uptake because, although the Vmax values for uptake and efflux are not significantly different, there is a 103−104 higher affinity for uptake of solute compared with efflux. Therefore, the SBP ABC transporters are able to support a substantial concentration gradient and provide a net uptake of solutes into bacterial cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2001.02497.x
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  • 2
    Electronic Resource
    Electronic Resource
    Nodulation of legumes by rhizobium (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 11 (1988), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. The formation of nitrogen-fixing nodules on leguminous plants is the culmination of an integrated development involving many plant and bacterial genes. This review focuses on the structure, function and regulation of the bacterial genes involved in the nodulation process. We attempt to interpret recent observations on these genes in the context of signal exchanges which occur between the macro-and micro-symbionts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1988.tb01364.x
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  • 3
    Electronic Resource
    Electronic Resource
    The vbs genes that direct synthesis of the siderophore vicibactin in Rhizobium leguminosarum: their expression in other genera requires ECF σ factor RpoI (2002)
    Oxford, UK : Blackwell Science Ltd.
    Molecular microbiology 44 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A cluster of eight genes, vbsGSO, vbsADL, vbsC and vbsP, are involved in the synthesis of vicibactin, a cyclic, trihydroxamate siderophore made by the symbiotic bacterium Rhizobium leguminosarum. None of these vbs genes was required for symbiotic N2 fixation on peas or Vicia. Transcription of vbsC, vbsGSO and vbsADL (but not vbsP) was enhanced by growth in low levels of Fe. Transcription of vbsGSO and vbsADL, but not vbsP or vbsC, required the closely linked gene rpoI, which encodes an ECF σ factor of RNA polymerase. Transfer of the cloned vbs genes, plus rpoI, to Rhodobacter, Paracoccus and Sinorhizobium conferred the ability to make vicibactin on these other genera. We present a biochemical genetic model of vicibactin synthesis, which accommodates the phenotypes of different vbs mutants and the homologies of the vbs gene products. In this model, VbsS, which is similar to many non-ribosomal peptide synthetase multienzymes, has a central role. It is proposed that VbsS activates L-N5-hydroxyornithine via covalent attachment as an acyl thioester to a peptidyl carrier protein domain. Subsequent VbsA-catalysed acylation of the hydroxyornithine, followed by VbsL-mediated epimerization and acetylation catalysed by VbsC, yields the vicibactin subunit, which is then trimerized and cyclized by the thioesterase domain of VbsS to give the completed siderophore.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.02951.x
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  • 4
    Electronic Resource
    Electronic Resource
    The products of Rhizobium genes, psi and pss, which affect exopolysaccharide production, are associated with the bacterial cell surface (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 5 (1991), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Translational fusions between a mutant phoA (lacking its promoter, ribosomal binding site and signal peptide sequence) and Rhizobium‘symbiotic’ genes were isolated. Since these fusions expressed alkaline phosphatase (AP), the product of phoA, the genes into which phoA was inserted apparently specify proteins located in the bacterial periplasm or cell membrane, the compartment in which AP has activity. These genes were psiA and genes upstream of psiA (psiA is required for normal nodule development and strains with multicopy psiA fall to make exopolysaccharide (EPS) and to nodulate). Fusions between phoA and pss (exo) genes, which are required for EPS production, also resulted in the expression of AP indicating that products of these pss genes were located at the cell surface. Using grus fusions to psiA and pssA, we found that the former was expressed in N2-fixing bean root nodules but the latter was not.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1991.tb02140.x
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  • 5
    Electronic Resource
    Electronic Resource
    Secretion of the Rhizobium leguminosarum nodulation protein NodO by haemolysin-type systems (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 6 (1992), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The Rhizobium leguminosarum biovar viciae nodulation protein NodO is partially homologous to haemolysin of Escherichia coli and, like haemolysin, is secreted into the growth medium. The NodO protein can be secreted by a strain of E. coli carrying the cloned nodO gene plus the haemolysin secretion genes hlyBD, in a process that also requires the outer membrane protein encoded by tolC. The related protease secretion genes, prtDEF, from Erwinia chrysanthemi also enable E. coli to secrete NodO. The Rhizobium genes encoding the proteins required for NodO secretion are unlinked to nodO and are unlike other nod genes, since they do not require flavonoids or NodO for their expression. Although proteins similar to NodO were not found in rhizobia other than R. leguminosarum bv. viciae, several rhizobia and an Agrobacterium strain containing the cloned nodO gene were found to have the ability to secrete NodO. These observations indicate that a wide range of the Rhizobiaceae have a protein secretion mechanism analogous to that which secretes haemotysin and related toxins and proteases in the Enterobacteriaceae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1992.tb02004.x
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  • 6
    Electronic Resource
    Electronic Resource
    Analysis of three nodD genes in Rhizobium leguminosarum biovar phaseoli; nodD 1 is preceded by nolE, a gene whose product is secreted from the cytoplasm (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 4 (1990), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In a strain of Rhizobium leguminosarum biovar phaseoli, three copies of the regulatory nodulation gene nodD were identified on the Sym plasmid and sequenced. Two were closely linked to each other and the third was near, but not adjacent, to the nodABC genes. Each of these nodD genes could correct the Nod defect of a nodD mutant strain of R. leguminosarum biovar viciae on peas. A truncated form of nodD2 could also correct this mutant, indicating that the C-terminus of NodD2 is not needed for inducing activity. Upstream of nodD1 and in the same operon is a newly described gene, nolE, whose product appears to be exported into the periplasm. Close to nodD2 is another gene, nolP, with no known counterpart in other rhizobia. Both nolP and nolE-nodD1 are preceded by ‘nod-box’ sequences and, in the former case, there appear to be two tandemly repeated nod-box sequences. Mutations in each of the nodD genes and in the nolE and nolP genes did not abolish nodulation or nitrogen fixation on beans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1990.tb00665.x
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  • 7
    Electronic Resource
    Electronic Resource
    Regulatory functions of the three nodD genes of Rhizobium leguminosarum biovar phaseoli (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 4 (1990), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The three nodD genes of a strain of Rhizobium leguminosarum biovar phaseoli were cloned to study their effects on transcription of themselves and of the nodC genes of biovars phaseoli and viciae. Efficient transcription of nodD1 required nodD1 and was enhanced by exposure of the cells to bean exudate consistent with the presence of a nod-box preceding the nolE-nodD1 operon. Transcription of nodD2 and nodDZ was constitutive. nodC of R. leguminosarum biovar phaseoli was activated by each of the nodD genes of that biovar in the absence of inducers but expression was enhanced in cells grown with bean exudate or the flavonoids genistein or naringenin. A mutant of nodD2, tacking 60bp at its 3’end, activated nodC in the presence of inducer, but was defective in regulating certain of the nodD genes. The nodC gene of R. leguminosarum biovar viciae responded differently to the various nodD genes of R. leguminosarum biovar phaseoli than did the nodC of the latter biovar.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1990.tb00666.x
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  • 8
    Electronic Resource
    Electronic Resource
    Transcription of rhiA, a gene on a Rhizobium leguminosarum bv. viciae Sym plasmid, requires rhiR and is repressed by flavanoids that induce nod genes (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 3 (1989), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Strains of Rhizobium leguminosarum biovar viciae specifically make an abundant protein (Rhi) in free-living culture but not in bacteroids. Genes needed for Rhi synthesis are on a Sym plasmid and here we show that one of these genes, rhiA, is the structural gene that specifies this polypeptide. Transcription of rhiA requires a regulatory gene, rhiR, located close to rhiA and to nod genes involved in nodulation. Mutations in rhiA or rhiR do not appear to affect symbiotic nitrogen fixation. Transcription of rhiA is repressed in cells grown in the presence of the flavanone hesperetin or the flavone apigenin, both of which are potent inducers of transcription of nod genes. This was deduced from the use of rhiA-lacZ fusions; however, when the Rhi polypeptide was detected in SDS gels, there was no apparent difference in the intensity of its staining in extracts obtained from cells grown with or without these flavanoid nod gene inducer molecules. However, a mutation in a nodulation gene, nolR, also closely linked to the nod and rhi genes, caused a severe depression in the amount of Rhi (as seen on gels) that was made in cells grown in the presence of inducer flavanoids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1989.tb00107.x
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  • 9
    Electronic Resource
    Electronic Resource
    Transcription of a Rhizobium ieguminosarum biovar phaseoli gene needed for melanin synthesis is activated by nifA of Rhizobium and Klebsiella pneumoniae (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 2 (1988), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The Rhizobium leguminosarum biovar phaseoli symbiotic plasmid pRP2JI carries a gene, melA, specifying the enzyme tyrosinase, which is responsible for the production of the pigment melanin in these bacteria. Transcription of melA is activated by the nifA gene of Rhizobium and, when the cloned melA gene is transferred to Escherichia coli, melA is expressed if the recipients contain nifA gene of Klebsiella pneumoniae. This nifA-dependent activation was temperature sensitive and required the ntrA gene. The cloned nifA gene of K. pneumoniae, when transferred to a nifA mutant of Rhizobium phaseoli biovar phaseoli, corrected the Mer− but not the Fix− phenotype. nifA of R. leguminosarum biovar phaseoli activated melA at higher levels in cells grown in low concentrations of oxygen. Also, nifA of fl. leguminosarum biovar phaseoli activated nifH of K. pneumoniae in Escherichia coli cells grown In low-oxygen concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1988.tb00036.x
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  • 10
    Electronic Resource
    Electronic Resource
    Single and multiple mutations affecting properties of the regulatory gene nodD of Rhizobium (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 3 (1989), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: nodD of Rhizobium leguminosarum has two regulatory properties: it autoregulates and, in cells grown with specific flavonoids, activates other nod genes. We isolated mutations in nodD affecting one or both properties. Those abolishing autoregulation and nod gene induction were at the 5′ end of nodD, as were those which only affected autoregulation. Mutations affecting nod gene activation are at the 3’end of nodD. Eleven mutations in this region of nodD were isolated: some had little effect on the regulatory properties; others reduced activation of other nod genes. 265 bps were removed from the 3’end of nodD: this abolished nodD function. Doubly mutant derivatives of nodD were constructed by making nodD genes with a mutation that conferred the ability to activate transcription of nod genes in the absence of inducers (class IV) plus another that abolished autoregulation and/or flavonoid-dependent nod gene activation. The behaviour of such double mutants was complex; e.g. in one case, a doubly mutant nodD gene containing the class IV mutation, coupled to one of those that (alone) abolished autoregulation and nod gene induction, was similar in behaviour to the wild type. In other cases, double mutants were similar to one of the parentals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1989.tb00142.x
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