Antioxidant enzyme activity in Acidithiobacillus ferrooxidans LR maintained in contact with chalcopyrite

The total protein content and activity of the enzymes glutathione reductase (GR), superoxide dismutase (SOD) and thioredoxin reductase (TrxR) were evaluated in Acidithiobacillus ferrooxidans LR cells maintained in contact with the metal sulfide chalcopyrite for 1 and 10 days. A significant decrease in total protein content was observed in cells maintained for 10 days in the presence of chalcopyrite, suggesting proteolytic breakdown due to exposure to the metal sulfide. Following 10 days of contact with chalcopyrite, increases in GR, SOD and TrxR activities were detected, suggesting the formation of reactive oxygen species. After ten days, there was a fivefold increase in GR activity, of which, isoenzyme IV represented approximately 82% of the total. An increase in Fe-SOD activity following ten days exposure to chalcopyrite was also determined, as measured on non-denaturing polyacrylamide gels. Also, after 10 days, an approximately 31-fold increase was observed for TrxR activity. The presence of oxidative stress when A. ferrooxidans is in the presence of chalcopyrite could have a negative impact on bioleaching.