A study of thermophilic aerobic sporeforming bacteria isolated from soil and water.

Abstract

Thirty-three strains of thermophilic aerobic sporeforming bacteria isolated from soil and water were studied by classical determinative bacteriological methods and by % guanine + cytosine (% GC) in the DNA. The cultures fell into two groups based upon % GC. There were 12 strains with % GC of 52–53.1 which were characteristic of Bacillus stearothermophilus. These strains were also classifiable as B. stearothermophilus by classical determinative bacteriological methods except three were aciduric. The other 21 strains had % GC ranging from 38.8 to 43.9 with a mean % GC of 42.04. Ten strains of the 21 could be B. coagulons by classical determinative bacteriological methods but not by % GC. The other 11 strains were not determinable by current classical determinative keys. These strains may be thermophilic variants of mesophilic species.