Salegentibacter profundi sp. nov. and Salegentibacter haimaensis sp. nov., isolated from deep-sea cold seep sediments of the South China Sea.

Two Gram-stain-negative, rod-shaped, facultatively anaerobic bacterial strains, designated F14T and HM20T, were isolated from deep-sea cold seep sediments in the South China Sea. Strain F14T grew at 4-40 ℃, pH 6.0-9.0 and in the presence of 0.5-10.0% (w/v) NaCl, while strain HM20T grew at 20-40 °C, pH 6.0-9.5 and with 0.5-8.0% (w/v) NaCl. Strains F14T and HM20T showed the highest sequence similarity with Salegentibacter flavus DSM 17794T (97.8%) and Salegentibacter sediminis K5023T (97.1%), respectively. Phylogenomic analysis based on core genome sequences supported their placement within the genus Salegentibacter. Average nucleotide identity and digital DNA-DNA hybridization values between the two novel strains and their closest phylogenetic relatives were below the species delineation thresholds of 95% and 70%, respectively. Chemotaxonomic analyses showed that the major cellular fatty acids were iso-C₁₅:₀, anteiso-C₁₅:₀ and iso-C₁₇:₀ 3-OH. The sole respiratory quinone detected was menaquinone-6, and the major polar lipid was phosphatidylethanolamine. The genomic DNA G+C contents of strains F14T and HM20T were 39.6% and 40.7%, respectively. In contrast to previously recognized species of the genus, both novel strains were able to grow under facultatively anaerobic conditions, which may be associated with environmental conditions in deep-sea cold seep sediments. Based on phenotypic, chemotaxonomic and genotypic results, strains F14T and HM20T represent two novel species of the genus Salegentibacter, for which the names Salegentibacter profundi and Salegentibacter haimaensis are proposed with the type strains F14T (=GDMCC 1.6178T=KCTC 102508T) and HM20T (=GDMCC 1.6269T=KCTC 102509T), respectively.