Free-Living
            <i>Rhizobium</i>
            Strain Able To Grow on N
            <sub>2</sub>
            as the Sole Nitrogen Source

Dreyfus, B; Elmerich, Claudine; Dommergues, Yvon

doi:10.1128/aem.45.2.711-713.1983

Cited by 158 publications

(37 citation statements)

References 7 publications

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“…The genotypes of the bacterial strains and plasmids used in this study are listed in Table 1. A. brasilense was grown at 33°C in Luria–Bertani (LB) medium supplemented with 2.5 mM CaCl 2 and 2.5 mM MgSO 4 [21] or minimal medium lactate (MML [22]). Escherichia coli strains were grown at 37°C in LB medium.…”

Section: Methodsmentioning

confidence: 99%

Disruption of dTDP-rhamnose biosynthesis modifies lipopolysaccharide core, exopolysaccharide production, and root colonization inAzospirillum brasilense

Jofré

Lagares

Mori

2004

FEMS Microbiology Letters

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The interaction between Azospirillum brasilense and plants is not fully understood, although several bacterial surface components like exopolysaccharides (EPS), flagella, and capsular polysaccharides are required for attachment and colonization. While in other plantb acteria associations (Rhizobium^legume, Pseudomonas^potato), lipopolysaccharides (LPS) play a key role in the establishment of an effective association, their role in the root colonization by Azospirillum had not been determined. In this study, we isolated a Tn5 mutant of A. brasilense Cd (EJ1) with an apparently modified LPS core structure, non-mucoid colony morphology, increased EPS production, and affected in maize root colonization. A 3790-bp region revealed the presence of three complete open reading frames designated rmlC, rmlB and rmlD. The beginning of a fourth open reading frame was found and designated rmlA. These genes are organized in a cluster which shows homology to the cluster involved in the synthesis of dTDP-rhamnose in other bacteria. Additionally, the analysis of the monosaccharide composition of LPSs showed a diminution of rhamnose compared to the wild-type strain. ß

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Section: Methodsmentioning

confidence: 99%

Disruption of dTDP-rhamnose biosynthesis modifies lipopolysaccharide core, exopolysaccharide production, and root colonization inAzospirillum brasilense

Jofré

Lagares

Mori

2004

FEMS Microbiology Letters

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“…Culture media used in this study were yeast extract mannitol (YM) [24] and yeast extract sodium lactate (YL) media [25]. The YL media was modified with considerably less P to avoid precipitation with Cd and with the trace elements ingredients omitted.…”

Section: Strains Of Rhizobia and Culture Mediummentioning

confidence: 99%

Responses of Azorhizobium caulinodans to cadmium stress

Zhengwei¹,

Fang²,

Lee³

et al. 2005

FEMS Microbiology Ecology

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The symbiosis of Azorhizobium caulinodans and an annul legume Sesbania rostrata was recently found to be tolerant to cadmium pollution by an unknown mechanism. In this study, A. caulinodans ORS571 and ZY-20 showed much stronger tolerance to cadmium than a mutant ORS571-X15 and a common Rhizobium sp., with minimum inhibitory concentration values as high as 4 and 5 mM (versus 1 and 0.1 mM) on yeast extract mannitol agar medium, respectively. Although Cd uptake by all three strains of A. caulinodans were mostly from absorption rather than binding (both loosely or tightly) on cell surface, in resistant strains a higher portion of extractable Cd was bound on the cell surface vs. absorbed (about 1:2.5 ratio) compared to the sensitive mutant (about 1:35.1 ratio). These results suggest that certain level of metal exclusion by a permeability barrier was involved in the mechanism of resistance to Cd by A. caulinodans ORS571 and ZY-20. Over the 12-h period of cultivation in yeast extract mannitol agar medium with Cd addition, the Cd concentrations in the outer membrane and periplasm and spheroplast were the highest at the first 3 h, and declined steadily over time. The fact that Cd concentrations in spheroplast of all three strains were many folds higher than those in outer membrane and periplasm, suggests that extracellular sequestration was not the only mechanism of Cd tolerance in A. caulinodans. The decline of Cd concentrations was significantly faster and started earlier in strains ORS571 and ZY-20 than in ORS571-X15. This suggests a second, probably more substantial, mechanism involves active transport of the metal from the cell, e.g., some efflux system for maintaining homeostasis under cadmium stress.

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“…Azorhizobium cauliriodans ORS57^ (Dreyfus etai., 1988; referred to as ORS571 in this manuscript) has the unusual capacity to grow on dinitrogen (N2) in the free-living state, as well as to fix nitrogen efficiently in nodules induced on the stem and roots of its host, the tropical legume Sesbania rostrata (Dreyfus and Dommergues, 1981; for a review, see de Bruijn, 1989). In addition, free-living nitrogen fixation by, and dinttrogen-dependent growth of, ORS571 in culture occurs at an unusually high temperature (37"C) and oxygen concentration (-3% O2 in the gas phase; Dreyfus et al, 1983;Gebhardt ef al., 1984). The regulatory circuitry controlling the expression of the ORS571 nitrogen fixation (nif, fix) genes in culture and in planta has been shown to have components in common with n//-regulatory elements specific for the free-living diazotroph Klebsiella pneumoniae, as weli as for different (Bradyfrhizobium species.…”

Section: Introductionmentioning

confidence: 99%

The Azorhizobium caulinodans nitrogen‐fixation regulatory gene, nifA, is controlled by the cellular nitrogen and oxygen status

Ratet¹,

Pawlowski²,

Schell³

et al. 1989

Molecular Microbiology

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Summary The nucleotrde sequence of the Azorhizobium caulinodans ORS571 nlfA locus was determined and the deduced NifA amino acid sequence compared with that of NifA from other nitrogen‐fixing species. Highly conserved domains, including helix‐turn‐helix and ATP‐binding motifs, and specific conserved residues, such as a cluster of cysteines, were identified. The nifA 5’upstream region was found to contain DNA sequence motifs highly homologous to promoter elements involved in nifAlntr‐mediated control and a consensus element found in the 5’upstream region of the Bradyrhizobium japonicum 5‐aminolevulinic acid synthase (hemA) gene and of Escherichia coli genes activated during anaerobiosis via the fnr (fumarate nitrate reduction) control system. A nifA‐lac fusion was constructed using miniMu‐lac and its activity measured in different genetic backgrounds and under various physiological conditions (in culture and in planta.) NifA expression was found to be negatively autoregulated, repressed by rich nitrogen sources and high oxygen concentrations, and controlled (partially) by the ntrC gene, both in culture and in planta. DNA supercoiling was also implicated in nifA regulation, since DNA gyrase inhibitors severely repressed nifA‐lac expression.

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Free-Living Rhizobium Strain Able To Grow on N ₂ as the Sole Nitrogen Source

Cited by 158 publications

References 7 publications

Disruption of dTDP-rhamnose biosynthesis modifies lipopolysaccharide core, exopolysaccharide production, and root colonization inAzospirillum brasilense

Disruption of dTDP-rhamnose biosynthesis modifies lipopolysaccharide core, exopolysaccharide production, and root colonization inAzospirillum brasilense

Responses of Azorhizobium caulinodans to cadmium stress

The Azorhizobium caulinodans nitrogen‐fixation regulatory gene, nifA, is controlled by the cellular nitrogen and oxygen status

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Free-Living Rhizobium Strain Able To Grow on N 2 as the Sole Nitrogen Source

Cited by 158 publications

References 7 publications

Disruption of dTDP-rhamnose biosynthesis modifies lipopolysaccharide core, exopolysaccharide production, and root colonization inAzospirillum brasilense

Disruption of dTDP-rhamnose biosynthesis modifies lipopolysaccharide core, exopolysaccharide production, and root colonization inAzospirillum brasilense

Responses of Azorhizobium caulinodans to cadmium stress

The Azorhizobium caulinodans nitrogen‐fixation regulatory gene, nifA, is controlled by the cellular nitrogen and oxygen status

Contact Info

Product

Resources

About

Free-Living Rhizobium Strain Able To Grow on N ₂ as the Sole Nitrogen Source