Metabolic changes of Acidithiobacillus caldus under Cu²(+) stress

Abstract

Metabolic changes were investigated by measuring the depletion of dissolved oxygen and the enzymatic activities of sulfur metabolism in Acidithiobacillus caldus (A. caldus) before and after copper stress. The results showed that high concentrations of Cu²(+) have an indirect negative effect on the sulfite oxidase and the APS reductase involved in sulfur metabolism when A. caldus is cultured in medium with elemental sulfur as its growth energy. This leads to a decrease in the respiration rate and the growth rate. The changes of activity are negatively correlated with the intracellular Cu²(+) concentration through an indirect interaction mechanism. A. caldus was able to induce an efflux of copper ions by forming an ATPase-dependent pump, which transported copper ions by consuming ATP. The negative effect of Cu²(+) on the bacterial metabolism could be minimized by the copper efflux when the bacteria were adapted in medium containing Cu²(+) for a long time. However, this bacterial rejuvenation became weaker when grown in medium containing higher concentrations of copper ions.