Rhizobium wuzhouense sp nov., isolated from roots of Oryza officinalis

Three bacterial isolates, designated W44(T), W15 and W11, were isolated from the root of Oryza officinalis grown in Wuzhou, China. These isolates were Gram-negative, aerobic, motile and rod-shaped; demonstrated cellulase and urea activities; and formed cream-coloured colonies. The 16S rRNA gene sequence analysis indicated that the similarities between strain W44(T) and strains W15 and W11 were 100 %; all of them belonged to the genus Rhizobium and had the highest sequence similarity to Rhizobium rosettiformans W3(T) (98.7 %), followed by Rhizobium ipomoeae shin9-1(T) (98.2 %). Sequencing of housekeeping genes (recA, atpD, rpoB and glnA) of the novel isolates revealed similarities to members of established Rhizobium species to be less than 94.3 %. The values of DNA-DNA hybridization between strain W44(T) and the reference strains (R. rosettiformans W3(T) and R. ipomoeae shin9-1(T)) were 41.3 and 29.2 %, respectively. The major cellular fatty acid of strain W44(T) was summed feature 8 (C-18 : 1 omega 9t and/or C-18 : 1 omega 9c and/or C-18 : 1 omega 7c). The polar lipid profile of strain W44(T) consisted of phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, two unidentified lipids and two unidentified aminophospholipids. The G+C content of strain W44(T) was 62.4 mol%. In nodulation tests, none of the three strains could induce nodule formation in Glycine max, Phaseolus vulgaris or Medicago sativa. The nodulation gene (nodA), nitrogenase reductase gene (nifH) and virulence gene (virC) were not detected by PCR in these strains. Based on the above results and phenotypic features, a novel species, Rhizobium wuzhouense sp. nov., is proposed, with strain W44(T) (=CCTCC AB 2017179(T)=GDMCC 1.1257(T)=KCTC 62194(T)) as the type strain.