Sulfide oxidation by spheroplasts of Thiobacillus ferrooxidans

Thiobacillus ferrooxidans is an acidophilic organism important to metal leaching of low-grade ores. The aforementioned importance is related to the ability of the bacterium to oxidize reduced iron and sulfur, principally found in nature as pyrite (FeS2). The present study dealt with sulfide oxidation at low pH values and the involvement of the cell envelope in the process of the inorganic oxidations. Sulfide oxidation was noted in spheroplasts of T. ferrooxidans prepared by enzymatic and chemical treatments and partially purified by differential centrifugation. No enzyme activities were noted in membrane fractions containing enrichments of lipopolysaccharide symbolic of outer membrane material or in membrane vesicles containing (or associated with) higher levels of proteins. Results to date indicate that in an acid milieu the envelope structure containing both the outer membrane and the intact inner cytoplasmic membrane is required for sulfide oxidation.