The gap gene of Rhizobium etli is required for both free life and symbiosis with common beans.

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH or Gap) is a ubiquitous enzyme essential for carbon and energy metabolism in most organisms. Despite its primary role in sugar metabolism, GAPDH is recognized for its involvement in diverse cellular processes, being considered a paradigm among multifunctional/moonlighting proteins. Besides its canonical cytoplasmic location, GAPDH has been detected on cell surfaces or as a secreted protein in prokaryotes, yet little is known about its possible roles in plant symbiotic bacteria.

Quantification of Mixed-Linkage β-Glucan (MLG) in Bacteria.

Prokaryotes are known to produce and secrete a broad range of biopolymers with a high functional and structural heterogeneity, often with critical duties in the bacterial physiology and ecology. Among these, exopolysaccharides (EPS) play relevant roles in the interaction of bacteria with eukaryotic hosts. EPS can help to colonize the host and assist in bacterial survival, making this interaction more robust by facilitating the formation of structured biofilms.

The Role of Two Linear β-Glucans Activated by c-di-GMP in CFN42.

Bacterial exopolysaccharides (EPS) have been implicated in a variety of functions that assist in bacterial survival, colonization, and host-microbe interactions. Among them, bacterial linear β-glucans are polysaccharides formed by D-glucose units linked by β-glycosidic bonds, which include curdlan, cellulose, and the new described Mixed Linkage β-Glucan (MLG). Bis-(3',5')-cyclic dimeric guanosine monophosphate (c-di-GMP) is a universal bacterial second messenger that usually promote EPS production.

Phylogenetic relationship of Lotus uliginosus symbionts with bradyrhizobia nodulating genistoid legumes.

Lotus species are legumes with potential for pastures in soils with low-fertility and environmental constraints. The aim of this work was to characterize bacteria that establish efficient nitrogen-fixing symbiosis with the forage species Lotus uliginosus. A total of 39 isolates were obtained from nodules of L.

Characterization of strains unlike Mesorhizobium loti that nodulate lotus spp. in saline soils of Granada, Spain.

Lotus species are forage legumes with potential as pastures in low-fertility and environmentally constrained soils, owing to their high persistence and yield under those conditions. The aim of this work was the characterization of phenetic and genetic diversity of salt-tolerant bacteria able to establish efficient symbiosis with Lotus spp. A total of 180 isolates able to nodulate Lotus corniculatus and Lotus tenuis from two locations in Granada, Spain, were characterized.

Genetic characterization of oligopeptide uptake systems in Sinorhizobium meliloti.

The genetic characterization of three ABC transport systems involved in oligopeptide uptake by Sinorhizobium meliloti is reported. Oligopeptide permease (Opp) encoded by the pSymB oppABCD operon, is required for uptake of tetrapeptides and certain tripeptides like 3Ala and bialaphos. The chromosomally encoded dipeptide permease (Dpp1), also able to import the toxic tripeptide bialaphos, is required for utilization of dipeptides and tripeptides like 3Gly and GlyGlyAla, with minor importance for utilization of 3Ala and tetrapeptides.

Role of potassium uptake systems in Sinorhizobium meliloti osmoadaptation and symbiotic performance.

Stimulation of potassium uptake is the most rapid response to an osmotic upshock in bacteria. This cation accumulates by a number of different transport systems whose importance has not been previously addressed for rhizobia. In silico analyses reveal the presence of genes encoding four possible potassium uptake systems in the genome of Sinorhizobium meliloti 1021: Kup1, Kup2, Trk, and Kdp.

Genetic diversity and host range of rhizobia nodulating Lotus tenuis in typical soils of the Salado River Basin (Argentina).

A total of 103 root nodule isolates were used to estimate the diversity of bacteria nodulating Lotus tenuis in typical soils of the Salado River Basin. A high level of genetic diversity was revealed by repetitive extragenic palindromic PCR, and 77 isolates with unique genomic fingerprints were further differentiated into two clusters, clusters A and B, after 16S rRNA restriction fragment length polymorphism analysis. Cluster A strains appeared to be related to the genus Mesorhizobium, whereas cluster B was related to the genus Rhizobium.

Sinorhizobium meliloti genes involved in tolerance to the antimicrobial peptide protamine.

The innate resistance of plants and animals to microbial infection is mediated in part by small cationic peptides with antimicrobial activity. We assessed the susceptibility of the alfalfa symbiont Sinorhizobium meliloti to the model antimicrobial peptide protamine. Twenty-one Tn5-induced mutants showing increased sensitivity to protamine were isolated, and nine were further characterized in detail.

The relaxase of the Rhizobium etli symbiotic plasmid shows nic site cis-acting preference.

Genetic and biochemical characterization of TraA, the relaxase of symbiotic plasmid pRetCFN42d from Rhizobium etli, is described. After purifying the relaxase domain (N265TraA), we demonstrated nic binding and cleavage activity in vitro and thus characterized for the first time the nick site (nic) of a plasmid in the family Rhizobiaceae. We studied the range of N265TraA relaxase specificity in vitro by testing different oligonucleotides in binding and nicking assays.

Identification of the rctA gene, which is required for repression of conjugative transfer of rhizobial symbiotic megaplasmids.

An analysis of the conjugative transfer of pRetCFN42d, the symbiotic plasmid (pSym) of Rhizobium etli, has revealed a novel gene, rctA, as an essential element of a regulatory system for silencing the conjugative transfer of R. etli pSym by repressing the transcription of conjugal transfer genes in standard laboratory media. The rctA gene product lacks sequence conservation with other proteins of known function but may belong to the winged-helix DNA-binding subfamily of transcriptional regulators.

Identification of functional mob regions in Rhizobium etli: evidence for self-transmissibility of the symbiotic plasmid pRetCFN42d.

An approach originally designed to identify functional origins of conjugative transfer (oriT or mob) in a bacterial genome (J. A. Herrera-Cervera, J.

Involvement of the Sinorhizobium meliloti leuA gene in activation of nodulation genes by NodD1 and luteolin.

The role of leucine biosynthesis by Sinorhizobium meliloti in the establishment of nitrogen-fixing symbiosis with alfalfa ( Medicago sativa) was investigated. The leuA gene from S. meliloti, encoding alpha-isopropylmalate synthase, which catalyses the first specific step in the leucine biosynthetic pathway, was characterized.