Rhizobium leguminosarum bv. viciae Exo- mutant strains RBL5523,exo7::Tn5,RBL5523,exo8::Tn5 and RBL5523,exo52::Tn5 are affected in nodulation and in the syntheses of lipopolysaccharide, capsular polysaccharide, and exocellular polysaccharide. These mutants were complemented for nodulation and for the syntheses of these polysaccharides by plasmid pMP2603. The gene in which these mutants are defec...

Carboxymethyl cellulase and polygalacturonase activities were evaluated in wild-type strains from different taxonomic groups of rhizobia which nodulate a specific range of legume hosts that do not normally overlap (R. meliloti, R. loti, R. leguminosarum biovar trifolii, R. leguminosarum biovar phaseoli, R. leguminosarum biovar viceae, and Bradyrhizobium japonicum). To detect these enzymatic act...

In wild-type Rhizobium leguminosarum, the sitABCD operon specifies a Mn(2+) transporter whose expression is severely reduced in cells grown in the presence of this metal. Mutations in the R. leguminosarum gene, mur (manganese uptake regulator), whose product resembles the Fur transcriptional regulator, cause high-level expression of sitABCD in the presence of Mn(2+). In gel-shift mobility assay...

The products of the Rhizobium leguminosarum hyp gene cluster are necessary for synthesis of a functional uptake [NiFe] hydrogenase system in symbiosis with pea plants, and at least for HypB and HypF, a role in hydrogenase-specific nickel metabolism has been postulated (L. Rey, J. Murillo, Y. Hernando, E. Hidalgo, E. Cabrera, J. Imperial, and T. Ruiz-Argüeso, Mol. Microbiol. 8:471-481, 1993). Th...

A quantitative method was developed to measure the binding of fluorescent-labeled lentil (Lens esculenta Moench), pea (Pisum sativum L.), broad bean (Vicia faba L.), and jackbean (Canavalia ensiformis L., DC.) lectins to various Rhizobium strains. Lentil lectin bound to three of the five Rhizobium leguminosarum strains tested. The number of lentil lectin molecules bound per R. leguminosarum 128...

Synthesis of the hydrogen uptake (Hup) system in Rhizobium leguminosarum bv. viciae requires the function of an 18-gene cluster (hupSLCDEFGHIJK-hypABFCDEX). Among them, the hupE gene encodes a protein showing six transmembrane domains for which a potential role as a nickel permease has been proposed. In this paper, we further characterize the nickel transport capacity of HupE and that of the tr...

The genetic structure of a population of nonsymbiotic Rhizobium leguminosarum strains was determined by the electrophoretic mobilities of eight metabolic enzymes. Nonsymbiotic strains were isolated from the rhizosphere of bean plants and characterized by growth on differential media and at different temperatures, intrinsic antibiotic resistance, the lack of homology to a nifH probe, and their i...

Congo red absorption is generally considered a contraindication of Rhizobium. However, R. leguminosarum takes up the dye on yeast extract-mannitol agar. The uptake of congo red varies among strains of R. leguminosarum, as shown elsewhere with strains of R. trifolii and R. meliloti. Congo red absorption does not distinguish rhizobia from other bacteria, but may be useful as a strain marker.

Flavonoids in root exudate of leguminous plants activate the transcription of Rhizobium genes involved in the formation of root nodules (nod genes). We report that inoculation with the homologous symbiont R. leguminosarum bv. viciae results in an increased nod gene-inducing activity (Ini) in root exudate of V. sativa subsp. nigra, whereas inoculation with heterologous Rhizobium strains results ...

DNA sequencing of the nodIJ region from Rhizobium leguminosarum biovar trifolii revealed the nodT gene immediately downstream of nodJ. DNA hybridizations using a nodT-specific probe showed that nodT is present in several R. leguminosarum strains. Interestingly, a flavonoid-inducible nodT gene homologue in R. leguminosarum bv. viciae is not in the nodABCIJ operon but is located downstream of nod...