[Genotypic and phenotypic polymorphism of environmental strains of the moderately thermophilic bacterium Sulfobacillus sibiricus].

Five cultures of moderately thermophilic spore-forming acidophilic chemolithotrophic bacteria were isolated from the zones of spontaneous heating of pyrrhotine-containing pyrite-arsenopyrite gold-arsenic sulfide ores in an operating open pit (strains B1, B2, B3, OFO, and SSO). Analysis of the chromosomal DNA structure revealed differences between these cultures at the strain level (apart from B3 and SSO, which had identical restriction profiles). All the strains had a similar G + C DNA molar content (47.4-48.3%). The level of DNA reassociation was 85 to 95%. The similarity between the DNA of the type strain Sulfobacillus sibiricus N1 isolated from arsenopyrite ore concentrate and that of these strains (83-93%) indicates that they belong to the same species. The strains had similar values of pH and temperature optimal for growth on ferrous iron (1.6-2.0 and 45-55 degrees C, respectively). They were mixotrophs; Fe(II), S0, and sulfide minerals along with organic compounds were used as energy sources and electron donors. However, the kinetic parameters of growth and substrate oxidation varied from strain to strain. Genetic variety of the strains from diverse ecosystems and environments is possibly the result of the different rates of microevolution processes.