Bacillus acidocaldarius sp.nov., an Acidophilic Thermophilic Spore-forming Bacterium

Summary: Fourteen cultures of thermophilic acidophilic bacteria have been isolated from a variety of thermal acid environments by enrichment at elevated temperatures and low pH. Morphological and physiological properties suggest that the bacteria are members of a homogeneous group of aerobic spore-forming rods. The base composition of the DNA is about 62 % guanine plus cytosine, and this fact together with the physiological properties suggests that relationship to other species in the genus Bacillus is rather distant. The isolates are hence classified in a new species, Bacillus acidocaldarius. The species is characterized by the ability to grow at temperatures from 45° to 70° (optimum 60° to 65°) and at pH values from 2·0 to 6·0 (optimum 3 to 4).