Rhizobium acidisoli sp nov., isolated from root nodules of Phaseolus vulgaris in acid soils

Two Gram-negative, aerobic, non-motile, rod-shaped bacterial strains, FH13(T) and FH23, representing a novel group of Rhizobium isolated from root nodules of Phaseolus vulgaris in Mexico, were studied by a polyphasic analysis. Phylogeny of 16S rRNA gene sequences revealed them to be members of the genus Rhizobium related most closely to Whizobium anhuiense' CCBAU 23252 (99.7 % similarity), Rhizobium leguminosarum USDA 2370(T) (98.6 %), and Rhizobium sophorae CCBAU 03386(T) and others (<= 98.3 %). In sequence analyses of the housekeeping genes recA, glnll and atpD, both strains formed a subclade distinct from all defined species of the genus Rhizobium at sequence similarities of 82.3-94.0 %, demonstrating that they represented a novel genomic species in the genus Rhizobium. Mean levels of DNA-DNA relatedness between the reference strain FH13(T) and the type strains of related species varied between 13.0 +/- 2.0 and 52.1 +/- 1.2 %. The DNA G+C content of strain FH13(T) was 63.5 mol% (T-m). The major cellular fatty acids were 16 : 0, 17 : 0 anteiso, 18 : 0, summed feature 2 (12 : 0 aldehyde/unknown 10.928) and summed feature 8 (18 : 1 omega 7c). The fatty acid 17 : 1 omega 5c was unique for this strain. Some phenotypic features, such as failure to utilize adonitol, L-arabinose, D-fructose and D-fucose, and ability to utilize D-galacturonic acid and itaconic acid as carbon source, could also be used to distinguish strain FH13(T) from the type strains of related species. Based upon these results, a novel species, Rhizobium acidisoli sp. nov., is proposed, with FH13(T) (=CCBAU 101094(T)=HAMBI 3626(T)=LMG 28672(T)) as the type strain