Rhizobium setariae sp. nov., an Indole-3-Acetic Acid-Producing Bacterium Isolated from Green Foxtail, Setaria viridis

A Gram-negative, indole-3-acetic acid-producing, aerobic, motile strain, designated as KVB221(T), was isolated from a green foxtail plant, Setaria viridis, from a park near the coast of Haeundae Beach, Busan, Republic of Korea. The 16S rRNA gene analysis revealed strain KVB221(T) to be a member of the genus Rhizobium, from which Rhizobium alvei TNR-22(T) (97.2%), Rhizobium daejeonense L61(T) (96.9%), and Rhizobium ipomoeae shin9-1(T) (95.7%) were selected for comparative analysis. Growth of the strain was observed at 10-50 degrees C (optimum 25-30 degrees C), at pH 5-10 (optimum pH 7), and in the presence of 0-8% NaCl (optimum 0%). The strain was observed to produce 36.3 +/- 0.8 mu g/ml of indole following 5 days of incubation. The major fatty acids are comprised of C-16:0, C-19:0 cyclo omega 8c, C-18:1 omega 7c, and the unresolved group summed feature 8 (C-18:1 omega 7c and/or C-18:1 omega 6c), while major polar lipids are identified as phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and phosphatidylmonomethylethanolamine (PME). The predominant quinone is Q-10 and the DNA G+C content of the strain is 59.3%. Based on publicly available genome data between strain KVB221(T) and its closely related strains, the average nucleotide identity and in silico DNA-DNA hybridization values ranged from 72.7 to 73.1 and 19.7 to 20.4%, respectively. Based on the chemotaxonomic, phenotypic, and genomic comparisons reported here, we propose Rhizobium setariae sp. nov. as a novel species belonging to the genus Rhizobium. The type strain is KVB221(T) (= KACC 21713(T) = NBRC 114644(T)).