Strain polymorphism of the plasmid profiles in Sulfobacillus species

Plasmids were discovered for the first time in strains belonging to different species of the genus Sulfobacillus: S. thermosulfidooxidans, S. sibiricus, S. thermotolerans, “S. olympiadicus”, and S. acidophilus. The plasmids were detected in the cells of four out of eight strains grown on a medium with ferrous iron. Adaptation to elementary sulfur was accompanied by changes in the plasmid profiles in two out of seven strains. Plasmids were detected in all the studied strains of sulfobacilli after adaptation to the pyrite-arsenopyrite ore concentrate from the Nezhdaninskoe deposit containing gold, silver, zinc, copper, and lead. No plasmids were found in S. thermotolerans Kr1^T after four transfers on a medium containing iron and 0.018 mM Ag⁺. After adaptation of the same strain to 765 mM Zn²⁺, only one plasmid was found in the cells, the largest among those detected earlier in this culture adapted to the Nezhdaninskoe ore concentrate. The strain S. thermotolerans Kr1^T, after four transfers on media with either 78 mM Cu²⁺ or 2 mM Pb²⁺, did not contain plasmids. The presence of plasmids in the cells of sulfobacilli did not influence their resistance to the ions of the studied metals.