Identity of Thermophilic Bacteria Isolated from Arctic Soils and Waters.

The most intensive study of the aerobic sporeforming bacteria (Smith et al., 1952) has revealed the lack of a clear-cut distinction between thermophilic and mesophilic species of the genus Bacius. It was found, however, that of the many cultures studied, only those belonging to the species BaciUlus stearotenwophilus would grow at 65 C. Some cultures of Bacillus coagulans, Bacius subtilie, Bacillus brevis, and BaciUus circulans would grow at 55 C, the incubation temperature commonly employed for cultivation of thermophiles. All of these species except B. stearotwmwphilus, however, could usually be grown at 28 C. This restriction of what might be called the "obligately thermophilic" aerobic spore-forming bacteria to a single species may have been due to the examination of cultures isolated from too restricted a range of environmental conditions. Because the cultures of thermophilic bacteria isolated by McBee and McBee (1956) from the Arctic region might be undescribed species, they were studied in detail using the classification tests recommended by Smith, et al., (1952).