Pheno- and genotypic characteristics of Acidithiobacillus ferrooxidans strains as affected by physicochernical properties of pyrites

Pyrites, which are the most widely spread sulfide minerals on the Earth and serve as substrates for chemolithoauthotrophic bacteria, substantially differ in their physicochemical, crystallochemical, and electrophysical properties. This paper has a focus on studying the dependence of phenotypic and genotypic characteristics in various Acidithiobacillus ferrooxidans strains upon the density, microhardness, total surface, presence of trace admixtures, conductivity type, resistance, and thermo electromotive force of pyrites. The studied A. ferrooxidans strains more efficiently oxidized pyrites with hole conductivity (p-type) than those of electron conductivity (n-type). During bacterial and chemical oxidation, some changes were observed in the electrophysical properties of pyrites (values of thermo electromotive force). A. ferrooxidans strain TFBk, isolated from the substrate of a more complex mineral composition, grew faster and more efficiently oxidized pyrites of both conductivity types than another strain TFV-1 isolated from a mineralogically simple ore. The most important role in bacterial oxidation of pyrites was played by redox potential of the growth medium when the concentration of the substrate exceeded 2%. Adaptation of A. ferrooxidans strains to pyrites of the both conductivity types was conjunct to changes in the chromosomal DNA structure and plasmid profiles. Taken together, the experimental data evidenced the influence of the physicochemical properties of utilized pyrites on the phenotypic and genotypic characteristics of A. ferrooxidans strains. (C) 2006 Elsevier B.V. All rights reserved.