Interaction of Chromosomal and Plasmid DNA in Acidithiobacillus ferrooxidans Strains Adapted to Different Oxidation Substrates

Restriction analysis of plasmids pTFK1 and pTFK2 of theAcidithiobacillus ferrooxidans strain TFBk was carried out, and the sizes of these plasmids were determined (13.5 and 30 kb, respectively). A macrorestriction map was built for plasmid pTFK1. DNA–DNA hybridization revealed that the plasmids contained homologous nucleotide sequences. Plasmid pTFK2 labeled with ³²P was used as a probe for Southern hybridization with blots of XbaI-generated fragments of the chromosomal DNA of A. ferrooxidans strains grown on a medium containing Fe²⁺ or adapted to different oxidation substrates. Low-intensity hybridization signals were observed for many fragments of the chromosomal DNA of the strains studied. In the process of adaptation to new oxidation substrates, the localization of bands producing the low-intensity hybridization signals changed in a number of cases. Certain fragments of the chromosomal DNA of the strains adapted to different oxidation substrates produced strong hybridization signals with pTFK2. The data obtained are discussed in terms of the possible role of IST elements and plasmids in the adaptation of A. ferrooxidans to new energy substrates, microevolution, and strain polymorphism.