Rhizobium oryziradicis sp. nov., isolated from rice roots

Two Gram-stain-negative, aerobic, rod-shaped endophytic bacterial strains, N19T and N11-2, were isolated from fresh rice (Oryza sativa) roots during investigation of the rice endophytic bacterial diversity. The 16S rRNA gene sequence results indicated that the similarity between strains N19T and N11-2 was 100 %. Both of them belong to the genus Rhizobium, with close similarity to Rhizobium taibaishanense CCNWSX 0483T (97.7 %), followed by Rhizobium vitis NCPPB 3554T (97.5 %). The sequence similarities of the housekeeping genes recA, gyrB and glnA between the novel isolates and members of the established species of the genus Rhizobium were less than 87 %. The DNA-DNA hybridization rates between strains N19T and N11-2 were 87.9 % using the initial renaturation rate method. Based on draft genome sequences, strain N19T showed 18.2 % and 19.6 % DNA-DNA hybridization values to R. taibaishanense CCNWSX 0483T and R. vitis S4, which demonstrated that these new isolates represent a novel species in the genus Rhizobium. The main cellular fatty acids were summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c). The DNA G+C content of strain N19T was 58.7 mol% (Tm). The polar lipid profile of N19T consisted of phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, an unknown lipid, two unknown aminolipids and an unidentified aminophospholipid. According to physiological and biochemical characteristics and genotypic data, strains N19T and N11-2 are considered to represent a novel species of the genus Rhizobium, for which the name Rhizobium oryziradicis sp. nov. is proposed, with N19T (=ACCC 19962T=KCTC 52413T) as the type strain.