STRUCTURAL-CHANGES IN THE CHROMOSOMAL DNA OF THIOBACILLUS-FERROOXIDANS CULTIVATED ON MEDIA WITH VARIOUS OXIDATION SUBSTRATES

The effects of oxidation substrates (ferrous iron, pyrite concentrate from the Angrenskoe ore deposit, arsenopyrite concentrate, and concent rates from the Olimpiadinskoe, Bakyrchikskoe, and Sayakskoe deposits) on the genomes of two Thiobacillus ferrooxidans strains of different o rigin were studied by pulsed-field gel electrophoresis of their chromo somal DNA digested with XbaI restriction endonuclease. In some cases, the adaptation of the cultures to new oxidation substrates was accompa nied by the appearance of new bands on the electrophoregrams of the DN A restriction digests or by the amplification of particular DNA fragme nts; the pattern of changes depended on the strain analyzed. Ten passa ges of strain VKM-458 on media with arsenopyrite or arsenopyrite-conta ining concentrates resulted in the amplification of a 28-kb DNA fragme nt, which persisted during ten subsequent passages on ferrous iron-con taining medium. Passages of strain TFBk on media containing pyrite, ar senopyrite, or concentrates from the Bakyrchikskoe and Sayakskoe depos its caused no changes in chromosomal DNA that could be registered by p ulsed-field gel electrophoresis of XbaI-digested chromosomal DNA. Chan ges in the restriction pattern did occur in strain TFBk adapted to gro wth on the concentrate from the Olimpiadinskoe deposit; these changes included the appearance of new 129-, 88-, and 77-kb DNA fragments and an increase in the quantity of a 186-kb fragment. However, after ten p assages of the concentrate-adapted culture of strain TFBk on ferrous i ron-containing medium, its DNA regained the initial restriction patter n.