Thalassococcus halodurans gen. nov., sp. nov., a novel halotolerant member of the Roseobacter clade isolated from the marine sponge Halichondria panicea at Friday Harbor, USA.

A Gram-negative, non-pigmented, ovoid-shaped, strictly aerobic, catalase- and oxidase-positive and highly halotolerant bacterial strain that was devoid of swimming and gliding motility, designated UST050418-052(T), was isolated from the surface of the marine sponge Halichondria panicea at Friday Harbor, WA, USA. Strain UST050418-052(T) required NaCl for growth and could tolerate salt concentrations of up to 18 %. The primary respiratory quinone was ubiquinone-10 and the DNA G+C content was 57.8 mol%. The predominant fatty acids were the saturated fatty acids 16 : 0 and 18 : 0 and the monounsaturated fatty acids 18 : 1 omega 7c and 18 : 1 omega 9c, altogether representing 82.9 % of the total. Phylogenetic analysis based on the 16S rRNA gene sequence placed UST050418-052(T) in a distinct lineage within the Roseobacter clade in the family Rhodobacteraceae, with 95.0-95.8 % sequence similarity to members of the nearest genus Thalassobius. The DNA-DNA relatedness between UST050418-052(T) and Thalassobius gelatinovorus IAM 12617(T) was 9 %. Strain UST050418-052(T) could be differentiated from closely related members of the Roseobacter clade by a number of chemotaxonomic and phenotypic characteristics such as its distinct fatty acid profile, ability to reduce nitrate to nitrite and inability to utilize citrate, succinate, L-arginine and pyruvate. Based on the phylogenetic, chemotaxonomic and phenotypic evidence presented in this study, we suggest that strain UST050418-052(T) represents a novel genus in the family Rhodobacteraceae. The name Thalassococcus halodurans gen. nov., sp. nov., is thus proposed. The type strain of Thalassococcus halodurans is UST050418-052(T) (=JCM 13833(T) =NRRL B-41465(T)).