SULFURISPHAERA OHWAKUENSIS GEN. NOV., SP. NOV., A NOVEL EXTREMELY THERMOPHILIC ACIDOPHILE OF THE ORDER SULFOLOBALES

Three spherical thermoacidophilic archaea (strains TA-1(T), TA-13, TA- 14) were obtained from acidic hot springs located in Ohwaku Valley, Ha kone, Japan. All the isolates are facultatively anaerobic, and grew op timally at around 85 degrees C, ph 2.0. Isolate TA-1(T) was characteri zed further. The G+C content of DNA from TA-1(T) is 33 mol%. Although these properties resemble those of the genus Acidianus, the sequence o f the 16S rRNA gene from strain TA-1(T) was more similar to that of sp ecies of Stygiolobus than of Acidianus. DNA-DNA hybridization experime nts also indicated that strain TA-1(T) is clearly distinguished phylog enetically from the members of Acidianus, Sulfolobus and Metallosphaer a. On the basis of the distinct physiological and molecular properties , we describe the new strains as members of the new genus Sulfurisphae ra. The type species of the genus is Sulfurisphaera ohwakuensis, and t he type strain of the species is TA-1(T) (= IFO 15161(T)).