Spirosoma profusum sp. nov., and Spirosoma validum sp. nov., radiation-resistant bacteria isolated from soil in South Korea

Two novel Gram-negative, rod-shaped bacterial strains BT702^T and BT704^T were isolated from soil collected in Jeongseon (37° 22′ 45″ N, 128° 39′ 53″ E), Gangwon province, South Korea. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strains BT702^T and BT704^T belong to distinct lineage within the genus Spirosoma (family Cytophagaceae, order Cytophagales, class Cytophagia and phylum Bacteroidetes). The strain BT702^T was closely related to Spirosoma flavus 15J11-2^T (96.7% 16S rRNA gene similarity) and Spirosoma metallilatum TX0405^T (93.3%). The strain BT704^T was closely related to Spirosoma koreense 15J8-5^T (94.6%), Spirosoma endophyticum DSM 26130^T (93.8%) and Spirosoma humi S7-4-1^T (93.8%). The genome sizes of type strains BT702^T and BT704^T are 8,731,341 bp and 8,221,062 bp, respectively. The major cellular fatty acids of strains BT702^T and BT704^T were C_16:1 ω5c and summed feature 3 (C_16:1 ω6c/C_16:1 ω7c). The strains were found to have the same quinone system, with MK-7 as the major respiratory quinone. The major polar lipids of strain BT702^T was identified to be phosphatidylethanolamine (PE), aminophospholipid (APL) and aminolipid (AL), while that of strain BT704^T consisted of phosphatidylethanolamine (PE) and aminophospholipid (APL). Based on the polyphasic analysis (phylogenetic, chemotaxonomic and biochemical), strains BT702^T and BT704^T can be suggested as two new bacterial species within the genus Spirosoma and the proposed names are Spirosoma profusum and Spirosoma validum, respectively. The type strain of Spirosoma profusum is BT702^T (=?KACC 22028^T?=?NBRC 114859^T) and type strain of Spirosoma validum is BT704^T (=?KACC 22030^T?=?NBRC 114966^T).