Generalized transduction in Rhizobium meliloti

Martin, Marie-Laure; Long, Sharon R.

doi:10.1128/jb.159.1.125-129.1984

Cited by 83 publications

(34 citation statements)

References 31 publications

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“…Microbiological techniques, complementation assays and plant tests were as described previously (Renalier et al, 1987). To obtain mutants affected in both copies of the reiteratedfix genes, pSym-located Tn5 insertions were transduced into GMI5595 using phage N3 (Martin and Long, 1984), and selected on streptomycin (400 iLg/ml). The position of TnS was verified by recombining TnS on pTH2 followed by restriction enzyme analysis of the pTH2-TnS derivatives (Batut et al, 1985).…”

Section: Methodsmentioning

confidence: 99%

“…The replicative form of M13MLD149 was linearized with EcoRI and ligated with an EcoRI to BamHI adaptor (Amersham) (before ligation, the adaptor was phosphorylated with T4 polynucleotide kinase). The ligation mixture was digested with BamHI and the 0.78 kb BamHI fragment was purified on an agarose gel Martin and Long (1984) and recombined into BamHI-cut pU 1363. After transformation of E. coli, recombinants were screened by colony hybridization using the purified EcoRI-BamHI-digested M13MLD149 insert as a probe.…”

Section: Construction Of the Pfixk -Lacz Fusion Plasmid Pjj5mentioning

confidence: 99%

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fixK, a gene homologous with fnr and crp from Escherichia coli, regulates nitrogen fixation genes both positively and negatively in Rhizobium meliloti.

et al. 1989

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Nitrogen fixation genes are shown to undergo a complex positive and negative regulation in Rhizobium meliloti. Activation of fixN by fixLJ is shown to require a third regulatory gene, fixK. As fixK is activated by fixLJ, we propose a cascade model for fixN regulation such that fixLJ activates fixN via fixK. In addition fixK negatively regulates expression of the nif‐specific activator nifA as well as its own expression by autoregulation. Thus nifA and fixK are subject to a mixed regulation, positive (by fixLJ) and negative (by fixK). The sequence of fixK shows homology with the Escherichia coli regulators fnr and crp, which makes fixK the third characterized member of this family of prokaryotic regulators.

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Section: Methodsmentioning

confidence: 99%

Section: Construction Of the Pfixk -Lacz Fusion Plasmid Pjj5mentioning

confidence: 99%

fixK, a gene homologous with fnr and crp from Escherichia coli, regulates nitrogen fixation genes both positively and negatively in Rhizobium meliloti.

et al. 1989

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“…Plasmids were transferred from E. coli to S. meliloti by triparental conjugation using the helper plasmid pRK600 (Finan et al, 1986). N3 phage transduction was performed as described (Martin and Long, 1984). Nodulation assays with alfalfa (Medicago sativa GT13Rplus) were performed as described (Oke and Long, 1999), on nitrogen-free BNM medium (Ehrhardt et al, 1992) with 1 mM of the ethylene inhibitor aminoisobutyrate (Sigma).…”

Section: Strains Media Growth Conditions and Genetic Techniquesmentioning

confidence: 99%

The periplasmic regulator ExoR inhibits ExoS/ChvI two‐component signalling in Sinorhizobium meliloti

Chen

Sabio

Long

2008

Molecular Microbiology

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SummarySinorhizobium meliloti requires ExoS/ChvI twocomponent signalling to establish a nitrogen-fixing symbiosis with legume hosts. The importance of ExoS/ChvI signalling in microbe-host interactions is underscored by the requirement of ExoS/ChvI orthologues for virulence of the related a-proteobacteria Agrobacterium tumefaciens and Brucella abortus. In S. meliloti, ExoS/ChvI is a key regulator of gene expression for exopolysaccharide synthesis, biofilm formation, motility, nutrient utilization and free-living viability. Previously, we showed that the novel conserved regulator ExoR interacts genetically with both ExoS and ChvI, and localizes to the periplasm of S. meliloti. Here, we show that ExoR physically associates with ExoS and that this association is important for regulating ExoS/ChvI signalling. We have identified point mutations in the Sel1-like repeat region of ExoR that disrupt binding to ExoS and cause a dramatic increase in ExoS/ChvI-dependent gene expression. Furthermore, we have found that physical interaction with ExoS stabilizes the ExoR protein. Together, our results indicate that ExoR binds to ExoS in the periplasm of S. meliloti to inhibit ExoS/ChvI activity, and that ExoR represents a novel periplasmic inhibitor of two-component signalling.

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“…Matings were set up on plain LB plates, and allowed to proceed overnight at 30°C, followed by isolation of transconjugants using appropriate antibiotic selection. Transduction was performed using phage N3, as described (Martin and Long, 1984).…”

Section: Bacterial Strains Growth Conditions and Routine Genetic Tecmentioning

confidence: 99%

A symbiotic mutant of Sinorhizobium meliloti reveals a novel genetic pathway involving succinoglycan biosynthetic functions

Griffitts

Long

2008

Molecular Microbiology

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SummaryA large-scale screen for symbiotic mutants was carried out using the model root nodulating bacterium Sinorhizobium meliloti. Several mutations in the previously uncharacterized gene msbA2 were isolated. msbA2 encodes a member of the ATPbinding cassette exporter family. This protein family is known to export a wide variety of compounds from bacterial cells. S. meliloti MsbA2 is required for the invasion of nodule tissue, with msbA2 mutant cells stimulating nodule primordium morphogenesis, but failing to invade plant tissue beyond the epidermal cell layer. msbA2 mutants do not exhibit any of the free-living traits often found to correlate with symbiotic defects, suggesting that MsbA2 may take part in a specifically symbiotic function. In strains that overproduce the symbiotic signalling polysaccharide succinoglycan, loss of MsbA2 function is extremely deleterious. This synthetic lethal phenotype can be suppressed by disrupting the succinoglycan biosynthetic genes exoY or exoA. It can also be suppressed by disrupting putative glycosyltransferase-encoding genes found upstream of msbA2. Finally, the symbiotic phenotype of a msbA2 null mutant is suppressed by secondary mutations in these upstream transferase genes, indicating that the msbA2 mutant phenotype may be caused by an inhibitory accumulation of a novel polysaccharide that is synthesized from succinoglycan precursors.

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Generalized transduction in Rhizobium meliloti

Cited by 83 publications

References 31 publications

fixK, a gene homologous with fnr and crp from Escherichia coli, regulates nitrogen fixation genes both positively and negatively in Rhizobium meliloti.

fixK, a gene homologous with fnr and crp from Escherichia coli, regulates nitrogen fixation genes both positively and negatively in Rhizobium meliloti.

The periplasmic regulator ExoR inhibits ExoS/ChvI two‐component signalling in Sinorhizobium meliloti

A symbiotic mutant of Sinorhizobium meliloti reveals a novel genetic pathway involving succinoglycan biosynthetic functions

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