Capsulimonas corticalis gen. nov., sp. nov., an aerobic capsulated bacterium, of a novel bacterial order, Capsulimonadales ord. nov., of the class Armatimonadia of the phylum Armatimonadetes.

Abstract

An aerobic bacterial strain designated AX-7T was isolated from the trunk surface of a Japanese beech (Fagus crenata). Cells of strain AX-7T were Gram-stain-negative, non-spore-forming, non-motile rods (1.0-1.2 µm in width and 1.2-3.0 µm in length) with peritrichous fimbriae. Cells were capsulated, and a number of them were surrounded by a thick slime layer. During growth, large aggregates formed, and the culture medium became viscous probably owing to exopolysaccharide release from the slime layer. The temperature range for growth was 10-37 °C, with an optimum at 30 °C. The pH range for growth was 5.0-7.0, with an optimum at pH 6.0. Strain AX-7T used various sugars, including polysaccharides, and yeast extract as growth substrates. Strain AX-7T contained menaquinones MK-9 and MK-10 as the respiratory quinones, and C16 : 1ω5c, C16 : 1ω11c, C16 : 0 and C14 : 0 as the major cellular fatty acids. Four unidentified phospholipids and 11 unidentified polar lipids constituted the polar lipids. The DNA G+C content was 61.0 mol%. The cell-wall peptidoglycan contained ll-diaminopimelic acid. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain AX-7T belonged to the class Armatimonadia, its closest relative being Armatimonas rosea YO-36T, with sequence similarity of 88.1%. Based on data from this polyphasic study, we propose that strain AX-7T represents a new genus of a novel species within the novel order Capsulimonadales ord. nov. of the class Armatimonadia, for which the name Capsulimonas corticalis gen. nov., sp. nov. is proposed. The type strain of C. corticalis is AX-7T (=DSM 105890T=NBRC 113044T).