Characterization of some thermophilic bacteria from the Hot Springs of Yellowstone National Park.

Extensive enzymatic studies have been conducted on cell-free fractions from a thermophilic bacterium designated as National Canners Association strain 2184 and tentativelv identified as Bacillus stearothermophilus Donk (1920), (Militzer et al., 1949, 1950, 1951, 1952; Georgi et al., 1951; h'Iarsh and Militzer, 1952). Preparatory to extending these investigations to other thermophilic bacteria, 24 strains of aerobic, sporeforming bacteria, which grew at 65 C or higher, were isolated from the thermal areas of Yellowstone National Park. Gordon and Smith (1949) in their taxonomic study of thermophilic bacteria reported that strains of B. stearoth.erinophilus were the only organisms in their collection capable of growth at 65 C. A preliminary attempt to characterize the Yellowstone strains, along with 6 National Canners Association strains, showed that a number of them differed significantly from the characters ascribed to B. stearothermophilus. The objectives of this paper are to report on the characterization of the Yellowstone isolates and to call attention to the possibility that sufficient differences may exist among strains of thermophilic bacteria capable of growth at 65 C to warrant definite strain, if not species, designation.