Kosmotoga arenicorallina sp. nov. a thermophilic and obligately anaerobic heterotroph isolated from a shallow hydrothermal system occurring within a coral reef, southern part of the Yaeyama Archipelago, Japan, reclassification of Thermococcoides shengliensis as Kosmotoga shengliensis comb. nov., and emended description of the genus Kosmotoga

摘要

A novel thermophilic and sulfur-reducing bacterium, strain S304T, was isolated from the Taketomi submarine hot spring shallow hydrothermal field located at southern part of the Yaeyama Archipelago, Japan. The cells were non-motile short thick rods or oval cocci 1.1–2.7 μm in length and 1.1–1.9 μm in width. Strain S304T was an obligately anaerobic heterotroph and sulfur reduction stimulates growth. Growth was observed between 50–65°C (optimum 60°C), pH 6.2–8.0 (optimum pH 7.1), 1.0–6.0% NaCl concentration (optimum 3.0%). The fatty acid composition was C_16:0 (71.4%), C_18:0 (20.9%) and C_18:1 (7.7%). The G + C content of genomic DNA was 40.8 mol%. The 16S rRNA gene sequence analysis indicated that strain S304T belonged to the genus Kosmotoga. Based on physiological and phylogenetic features of a new isolate, we propose new species in the genus Kosmotoga: the type strain of Kosmotoga arenicorallina sp. nov is S304T (=JCM 15790T = DSM22549T). Thermococcoides shengliensis 2SM-2T is phylogenetically associated with Kosmotoga olearia 14.5.1T. Based on the phylogenetic relationship between Thermococcoides shengliensis 2SM-2T and Kosmotoga olearia 14.5.1T, we propose the reclassification of Thermococcoides shengliensis as Kosmotoga shengliensis comb. nov. (type strain 2SM-2T). In addition, an emended description of the genus Kosmotoga is proposed.