Rhizobium rhizoryzae sp. nov., isolated from rice roots

Abstract

Two strains (J3-AN59T and J3-N84) of Gram-stain-negative, aerobic and rod-shaped bacteria were isolated from the roots of fresh rice plants. The 16S rRNA gene sequence similarity results showed that the similarity between strains J3-AN59T and J3-N84 was 100 %. Both strains were phylogenetically related to members of the genus Rhizobium , and they were most closely related to Rhizobium tarimense ACCC 06128T (97.43 %). Similarities in the sequences of housekeeping genes between strains J3-AN59T and J3-N84 and those of recognized species of the genus Rhizobium were less than 90 %. The polar lipid profiles of both strains were predominantly composed of phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and an unknown aminophospholipid. The major cellular fatty acids were summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) and C16 : 0. The DNA G+C contents of J3-AN59T and J3-N84 were 55.7 and 57.1 mol%, respectively. The DNA–DNA relatedness value between J3-AN59T and J3-N84 was 89 %, and strain J3-AN59T showed 9 % DNA–DNA relatedness to R. tarimense ACCC 06128T, the most closely related strain. Based on this evidence, we found that J3-AN59T and J3-N84 represent a novel species in the genus Rhizobium and we propose the name Rhizobium rhizoryzae sp. nov. The type strain is J3-AN59T ( = ACCC 05916T = KCTC 23652T).