Isolation and preliminary taxonomic studies of Thermus strains isolated from Yellowstone National Park, USA.

Forty-eight strains of Thermus isolated from hot springs in Yellowstone National Park, Wyoming, USA, and eight reference strains were subjected to a numerical taxonomic analysis using Gower's coefficient (SG) with single and average linkage clustering. Two major groups were distinguished, which could be differentiated by colony morphology, ability to reduce nitrate and proteolytic activity. Cluster 1 contained Thermus aquaticus YT-1, the type strain of the species, and cluster 2 contained authentic strains of 'T. flavus' and 'T. thermophilus'. T. ruber was recovered as a single member cluster. The mol % G + C of DNA from representative strains from each cluster was 64.4 to 66.8 for cluster 1, 62.2 to 67.1 for cluster 2 and 62.5 for T. ruber.