Abstract
Numerous streptomycete strains were isolated from soil samples collected from several extreme environments in Yunnan, China, in recent years. These strains are alkalophiles, acidophiles, thermophiles or psychrophiles. Some of them were compared with Streptomyces from common environments and 8 other genera of Actinomycetales with cell wall types I, II, III, and IV. In total, 73 strains were studied. The relationships of these strains using 66 unit characters were analysed by Ssm coefficient and clustering by UPGMA algorithm. Cluster thermophile, cluster psychrophile, cluster alkalophile and cluster acidophile were distinguished at the 67% Ssm similarity level. The authors proposed that thermophilic (growth at 65°C), psychrophilic (optimum growth at 10 to 15°C, growth at 0°C, no growth at 28°C), acidophilic (optimum growth at pH 3 to 4) and alkalophilic (optimum growth at pH 10) streptomycetes should be regarded as independent species-groups. When a numerical classification of Streptomyces is made, growth temperatures and optimum pHs for strains can be selected as diagnostically valuable characters for clustering.
