Spirosoma radiotolerans sp. nov., a Gamma-Radiation-Resistant Bacterium Isolated from Gamma Ray-Irradiated Soil

A Gram-negative, short-rod-shaped bacterial strain with gliding motility, designated as DG5Aᵀ, was isolated from a rice field soil in South Korea. Phylogenic analysis using 16S rRNA gene sequence of the new isolate showed that strain DG5Aᵀ belong to the genus Spirosoma in the family Spirosomaceae, and the highest sequence similarities were 95.5 % with Spirosoma linguale DSM 74ᵀ, 93.4 % with Spirosoma rigui WPCB118ᵀ, 92.8 % with Spirosoma luteum SPM-10ᵀ, 92.7 % with Spirosoma spitsbergense SPM-9ᵀ, and 91.9 % with Spirosoma panaciterrae Gsoil 1519ᵀ. Strain DG5Aᵀ revealed resistance to gamma and UV radiation. Chemotaxonomic data showed that the most abundant fatty acids were summed feature C₁₆:₁ ω7c/C₁₆:₁ ω6c (36.90 %), C₁₆:₁ ω5c (29.55 %), and iso-C₁₅:₀ (14.78 %), and the major polar lipid was phosphatidylethanolamine (PE). The DNA G+C content of strain DG5Aᵀ was 49.1 mol%. Together, the phenotypic, phylogenetic, and chemotaxonomic data supported that strain DG5Aᵀ presents a novel species of the genus Spirosoma, for which the name Spirosoma radiotolerans sp. nov., is proposed. The type strain is DG5Aᵀ (=KCTC 32455ᵀ = JCM19447ᵀ).