Effect of Light Metal Ions and Chloride on Activity of Moderately Thermophilic Acidophilic Iron-Oxidizing Microorganisms

Abstract

The effect of sodium, potassium, magnesium, and aluminum ions, as well as of the chloride ion on the growth and ferrous iron oxidation by moderately thermophilic acidophilic iron-oxidizing microorganisms was studied. Strains of the microorganisms predominant in biohydrometallurgical processes (bacteria of genus Sulfobacillus and archaea of the genus Acidiplasma) were the subjects of the study. Ability of the studied strains to grow and oxidize ferrous iron in the media containing different concentrations of sodium, potassium, magnesium, and aluminum (up to 1000 mM) was determined. The experiments were conducted in two variants, in which the studied metals were added to the medium as sulfates and chlorides, respectively. It was revealed that inhibitory effects of the studied metals on the studied strains differed insignificantly and that high concentrations all studied salts inhibited growth and ferrous iron oxidation. The studied Acidiplasma strains were shown to be more tolerant to the cations than the Sulfobacillus strains. The inhibitory effect of chloride ion on the studied strains was the most significant, which were probably adapted to the habitats characterized by high concentrations of metals and sulfates, but not of chloride ions. The mechanisms of action of the studied light metal ions on growth of iron-oxidizing acidophilic microorganisms are discussed.