The detailed structure of the symbiotically important exopolysaccharide succinoglycan from Rhizobium meliloti Rm1021 was determined by mass spectrometry with electrospray ionization and collision-induced dissociation of the octameric oligosaccharide repeating unit. Previously undetermined locations of the succinyl and acetyl modifications were determined, in respect to both residue locations wi...

A circular linkage map of the Rhizobium meliloti megaplasmid pRmeSU47b was constructed. The map consists of transposon insertions carrying alternating antibiotic resistance markers linked by phi M12 transduction. Data from conjugation experiments utilizing donor strains carrying Tn5-oriT insertions in the megaplasmid supported the proposed genetic map. In addition, the positions of previously i...

To investigate the expression of specific symbiotic genes during the development of nitrogen-fixing root nodules, we conducted a systematic analysis of nodule-specific proteins and RNAs produced after the inoculation of alfalfa roots with a series of Rhizobium meliloti mutants generated by site-directed transposon Tn5 mutagenesis. The mutagenized region of the Rhizobium genome covered approxima...

We approached the identification of Ensifer (Sinorhizobium) meliloti conjugal functions by random Tn5-B13 mutagenesis of the pSmeLPU88a plasmid of E. meliloti strain LPU88 and the subsequent selection of those mutants that had lost the ability to mobilize the small plasmid pSmeLPU88b. The Tn5-B13-insertion site of one of the mutants was cloned as an EcoRI-restricted DNA fragment that after subs...

The bacterium Rhizobium meliloti forms N2-fixing root nodules on alfalfa plants. The ndvF locus, located on the 1,700-kb pEXO megaplasmid of R. meliloti, is required for nodule invasion and N2 fixation. Here we report that ndvF contains four genes, phoCDET, which encode an ABC-type transport system for the uptake of Pi into the bacteria. The PhoC and PhoD proteins are homologous to the Escheric...

The phylogenetic relatedness among 12 agriculturally important species in the order Rhizobiales was estimated by comparative 16S rRNA and dnaK sequence analyses. Two groups of related species were identified by neighbor-joining and maximum-parsimony analysis. One group consisted of Mesorhizobium loti and Mesorhizobium ciceri, and the other group consisted of Agrobacterium rhizogenes, Rhizobium ...

Rhizobium meliloti Nod(-) mutant WL131, a derivative of wild-type strain 102F51, was complemented by a clone bank of wild-type R. meliloti 1021 DNA, and clone pRmJT5 was recovered. Transfer of pRmJT5 conferred alfalfa nodulation on other Rhizobium species, indicating a role in host range determination for pRmJT5. Mutagenesis of pRmJT5 revealed several segments in which transposon insertion caus...

A 47-base-pair (bp) conserved sequence in the 5'-flanking regions of three transcriptional units coding for nodulation functions (nodABC, nodEFG, and nodH) has been identified in Rhizobium meliloti strain 41. The conserved region contains subsequences of 7 bp, 5 bp, and 25 bp. The conserved 25-bp sequence was synthesized and used as a hybridization probe; three additional copies of the sequence...