A new Rhizobium species isolated from the water of a crater lake, description of Rhizobium aquaticum sp. nov.

A novel isolate, strain SA-276, was isolated from the water of Lake St. Ana, a crater lake which is located in Romania. Phylogenetic analysis based on the 16S rRNA gene revealed that the new strain is a member of the family Rhizobiaceae, showing a high pairwise similarity value (97.65%) to Rhizobium tubonense CCBAU 85046 (= DSM 25379), Rhizobium leguminosarum USDA 2370 (= LMG 14904), Rhizobium anhuiense CCBAU 23252 and Rhizobium laguerreae FB206. Cells of strain SA-276 were rod-shaped, motile, oxidase negative and weakly catalase positive. The predominant fatty acids were Cω7c and cyclo Cω8c, the major respiratory quinones were Q-10 and Q-9, and the main polar lipids were phosphatidylmonomethylethanolamine, phosphatidylglycerol and phosphatidylcholine. The G + C content of the genomic DNA of strain SA-276 was 60.8 mol%. The novel isolate can be distinguished from the closest related type strain R. tubonense DSM 25379 based on its broader substrate specificity and positive trypsin enzyme activity. On the basis of the phenotypic, chemotaxonomic and molecular data, strain SA-276 is considered to represent a new species, for which the name Rhizobium aquaticum sp. nov. is proposed. The type strain is SA-276 (= DSM 29780 = JCM 31760).