Mesorhizobium microcysteis sp. Nov., isolated from a culture of microcystis aeruginosa

Abstract

Strain MaA-C15T, a Gram-stain-negative, non-spore-forming and strictly aerobic bacterium, was isolated from a xenic culture of Microcystis aeruginosa in the Republic of Korea. Cells were motile rods showing positive reactions in catalase and oxidase tests. Growth was observed between 15 and 37 °C (optimum, 30 °C), between pH 6.0 and pH 11.0 (optimum, pH 7.5) and in the presence of 0–2.0% (w/v) NaCl (optimum, 0%). Strain MaA-C15T contained C16:0, 11-methyl-C18:1 ω7c, cyclo-C19:0 ω8c and summed feature 8 (C18:1 ω6c and/or C18:1 ω7c) as the major cellular fatty acids and ubiquinone-10 as the sole respiratory quinone. Phosphatidy-lethanolamine, phosphatidylmonomethylethanolamine, an unidentified aminophospholipid, an unidentified glycolipid and three unidentified phospholipids were detected as the major polar lipids. The G+C content of the genomic DNA was 64.1 mol%. Phy-logenetic and phylogenomic analyses based on 16S rRNA gene and genome sequences revealed that strain MaA-C15T formed a phyletic lineage with Mesorhizobium sediminum YIM M12096T within the family Phyllobacteriaceae. Strain MaA-C15T was most closely related to Mesorhizobium albiziae DSM 21822T with a 98.2% 16S rRNA sequence similarity. Average nucleotide identity and in silico DNA–DNA hybridization values between strain MaA-C15T and M. albiziae DSM 21822T were 75.4 and 20.1%, respectively. Based on the results of phenotypic, chemotaxonomic and molecular analyses, strain MaA-C15T represents a novel species of the genus Mesorhizobium, for which the name Mesorhizobium microcysteis sp. nov. is proposed. The type strain is MaA-C15T (=KACC 21226T=JCM 33503T). © 2021, Microbiology Society. All rights reserved.