Description and genomic characterization of Mesorhizobium marinum sp. nov., a bacterium isolated from sea sediment

Two Gram-stain-negative, aerobic strains, designed ZMM04-4^T and ZMM04–5, were isolated from sea sediment collected from Qinzhou Bay, Guangxi Zhuang Automous Region, China. The predominant respiratory quinone was ubiquinone-10. The polar lipids were identified as diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, aminophospholipid and phospholipid. The predominant fatty acids were C_18:1ω7c, C_19:0 cyclo ω8c and C_16:0. Strain ZMM04-4^T shared 99.7 % similarity of 16S rRNA gene sequence with ZMM04–5. The digital DNA-DNA hybridization and average nucleotide identity values between strain ZMM04-4^T and ZMM04–5 were 92.9 % and 98.6 %, respectively, indicating that strains ZMM04-4^T, ZMM04–5 belong to the same species. Phylogenetic and phylogenomic analysis indicated that strains ZMM04-4^T and ZMM04–5 belong to the genus Mesorhizobium and showed the highest sequence similarity to Mesorhizobium qingshengii CGMCC 1.12097^T (97.7 %–97.8 % sequence similarity) and Mesorhizobium shangrilense DSM 21850^T (97.7 %–97.8 %). The average nucleotide identity and digital DNA-DNA hybridization values between strains ZMM04-4^T, ZMM04–5 and their closely related species were within the ranges of 76.5 %–77.2 % and 20.9 %–21.8 %, respectively, indicating that strains ZMM04-4^T, ZMM04–5 were novel species. In accordance with phylogenetic and genomic as well as phenotypic and chemotaxonomic characterizations, strains ZMM04-4^T and ZMM04–5 should be assigned to the genus Mesorhizobium and indentified as a novel species, for which the name Mesorhizobium marinum sp. nov., is proposed. The type strain is ZMM04-4^T (=MCCC 1K08883^T = KCTC 8273^T).