Thermophagus xiamenensis gen. nov., sp. nov., a moderately thermophilic and strictly anaerobic bacterium isolated from hot spring sediment

Abstract

A moderately thermophilic and strictly anaerobic bacterium, designated HS1T, was isolated from offshore hot spring sediment in Xiamen, China. Cells were Gram-negative, catalase-positive, oxidase-negative, slender and flexible rods without flagella. The strain could grow at 35–55 °C (optimum at 50 °C) and in 1–8 % NaCl (w/v; optimum 2–4 %). Phylogenetic analysis based on 16S rRNA gene sequences showed that strain HS1Twas affiliated with the familyMarinilabiliaceaeand shared a distant relationship with the previously described genera. The isolate was most closely related toAnaerophaga thermohalophilaFru22Twith 16S rRNA gene sequence similarity of 92.4 %, followed by the other members of the familyMarinilabiliaceaewith 88.7–91.1 % similarity. The dominant cellular fatty acids were iso-C15 : 0and anteiso-C15 : 0. The predominant quinone was MK-7. The major polar lipids were phosphatidylethanolamine (PE) and an unknown polar lipid. The genomic DNA G+C content was 38.7 mol%. Besides the phylogenetically distant relationship, strain HS1Twas obviously distinguished from the most closely related genera in several phenotypic properties including colony colour and pigment production, optimal temperature, optimal NaCl, relation to O2, bicarbonate/carbonate requirement, catalase activity, nitrate reduction, fermentation products and cellular fatty acid profile. Based on the phenotypic and phylogenetic data, strain HS1Trepresents a novel species of a new genus, for which the nameThermophagus xiamenensisgen. nov., sp. nov. is proposed. The type strain of the type species is HS1T( = DSM 19012T = CGMCCC 1.5071T).