Physiological Characteristics of a New Thermophilic Obligately Chemolithotrophic Thiobacillus Species, Thiobacillus tepidarius

We describe a new Thiobacillus species which is a gram-negative, motile, rod-shaped organism having polar flagella. The optimum growth temperature is 43 to 45°C, and the optimum pH range is 6.0 to 7.5. This organism is obligately chemolithotrophic and autotrophic and has ribulose bisphosphate carboxylase activity. It is able to oxidize thiosulfate, trithionate, tetrathionate, hexathionate, heptathionate, sulfur, and sulfide, but is not able to use sulfite, thiocyanate, or dithionate for growth. In batch culture it converts thiosulfate to tetrathionate during or before growth. It has both rhodanese and thiosulfate-oxidizing enzyme activites. It does not grow anaerobically with nitrate or nitrous oxide on either thiosulfate or tetrathionate. The guanine-plus-cytosine content of its deoxyribonucleic acid is 66.6 mol%, and it contains ubiquinone Q-8 in its respiratory chain. The organism is named Thiobacillus tepidarius sp. nov. The type strain is strain DSM 3134, which has been deposited in the Deutsche Sammlung von Mikroorganismen, Göttingen, Federal Republic of Germany.