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

A novel isolate, strain SA-276 ^T , 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 ^T (= DSM 25379 ^T ), Rhizobium leguminosarum USDA 2370 ^T (= LMG 14904 ^T ), Rhizobium anhuiense CCBAU 23252 ^T and Rhizobium laguerreae FB206 ^T . Cells of strain SA-276 ^T were rod-shaped, motile, oxidase negative and weakly catalase positive. The predominant fatty acids were C _18:1 ω7c and cyclo C _19:0 ω8c, 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 ^T was 60.8 mol%. The novel isolate can be distinguished from the closest related type strain R. tubonense DSM 25379 ^T based on its broader substrate specificity and positive trypsin enzyme activity. On the basis of the phenotypic, chemotaxonomic and molecular data, strain SA-276 ^T is considered to represent a new species, for which the name Rhizobium aquaticum sp. nov. is proposed. The type strain is SA-276 ^T (= DSM 29780 ^T  = JCM 31760 ^T ).