Mesorhizobium sediminum sp. nov., isolated from deep-sea sediment

Abstract

A novel Gram-staining-negative, short rod, non-motile, non-spore-forming, aerobic bacterium, designated strain YIM M12096T, was isolated from deep-sea sediment collected from the Indian Ocean. Optimal growth conditions of the strain were observed at 25？30 °C, pH 6.0 and in the presence of 3？5% (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain YIM M12096T was closely related to Nitratireductor indicus C115T (97.4% 16S rRNA gene sequence similarity) and Mesorhizobium thiogangeticum SJTT (97.3%). The strain, however, formed a robust clade with members of the genus Mesorhizobium in phylogenetic dendrograms generated with neighbour-joining, maximum-likelihood and maximumparsimony trees. Analysis based on the sequence of housekeeping gene recA also gave a similar phylogenetic relationship, indicating that strain YIM M12096T is a member of the genus Mesorhizobium. DNA？DNA relatedness values between strain YIM M12096T and related type strains N. indicus CCTCC AB209298T and M. thiogangeticum DSM 17097T were 40.5% and 36.7%, respectively. Chemotaxonomic features of the isolate included phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, an unidentified aminophospholipid and an unidentified phospholipid as its characteristic polar lipids and Q-10 as respiratory ubiquinone. Major fatty acids (>10%) detected were C18: 1ω7c and/or C18: 1ω6c, 11-methyl-C18: 1ω7c and cyclo-C19: 0ω8c. Based on the chemotaxonomic properties and phylogenetic analyses, strain YIM M12096T is determined to be a member of the genus Mesorhizobium. The strain could be differentiated from the closely related species by the differences in physiological and biochemical properties supported by low DNA？DNA relatedness values. It is therefore concluded that strain YIM M12096T represents a novel species of the genus Mesorhizobium, for which the name Mesorhizobium sediminum sp. nov. is proposed. The type strain is YIM M12096T (=CCTCC AB 2014219T=KCTC 42205T).