[Strain polymorphism of the plasmid profiles in Acidithiobacillus ferrooxidans]

Plasmid profiles were studied in 27 Acidithiobacillus ferrooxidans strains isolated from different geographic zones and substrates differing in the composition of the main sulfide minerals, and also in experimentally obtained strains with acquired enhanced resistance to the ions of heavy metals (Fe, Ni, Cu, Zn, As). In 16 out of 20 strains isolated from different substrates, one to four 2- to 20-kb and larger plasmids were revealed. Plasmids were found in all five strains isolated from gold-containing pyrite-arsenopyrite ores and concentrates, in nine of 11 strains isolated from the ores and concentrates containing nonferrous metals, and in two of four strains isolated from the oxidation substrates of simple composition (mine waters, pyritized coals, active sludge). Changes in the plasmid profiles in some A. ferrooxidans strains (TFZ, TFI-Fe, TFV-1-Cu) with experimentally enhanced resistance to Zn2+, Fe3+, and Cu2+, respectively, were noted as compared with the initial strains. After 30 passages on S0-containing medium, strain TFBk showed changes in the copy number of plasmids. The role of plasmids in the processes of oxidation of energy substrates and in the acquired enhanced resistance to the heavy metal ions is discussed.