Isolation and characterization of a moderately thermophilic sulphur-oxidizing bacterium

A moderately thermophilic sulphur-oxidizing bacterium was isolated from water of the Goshiki hot spring in Hokkaido, Japan, and designated strain GO-1. It was a Gram-negative, nonspore-forming, nonmotile, and rod-shaped bacterium, which had an optimum temperature and pH for growth at 45°C and pH 2, respectively. The mean G + C content of the DNA was 64.8 mol%, and the strain utilized sulphur and tetrathionate as a sole energy source. Strain GO-1 did not utilize Fe²⁺ as a sole energy source, and fixed carbon dioxide in sulphur medium, indicating that strain GO-1 was an obligately chemolithoautotrophic bacterium. The 16S rRNA analysis indicated that strain GO-1 manifested a close relationship with Thiobacillus caldus KU. Some characteristics of strain GO-1 were different from those of T. caldus KU, and consequently it is suggested that strain GO-1 belongs to a new strain of Thiobacillus caldus.