Expression of the rus gene encoding rusticyanin in Acidithiobacillus ferrooxidans ATCC33020

摘要

Among the bioleaching microorganisms, Acidithiobacillus ferrooxidans is one of the most studied. Even though several electron transfer proteins have been identified, there is no convincing argument to tell in which respiratory chain these proteins are involved. Rusticyanin is the At. ferrooxidans redox protein which has been the most extensively studied. This periplasmic blue copper protein is generally considered to play a pivotal role in ferrous oxidation because of its concentration (up to 5% of total soluble proteins) when the cells are grown on iron medium. However, this essential role has been contested (1). To gain more insight into the conditions during which rusticyanin is synthesized, we have studied rusgene expression at the transcriptional and at the translational level. In the At. ferrooxidans ATCC33020 strain, rusticyanin was present in ferrous iron conditions throughout all growth phases while in sulfur conditions, rusticyanin was present only during the exponential phase and disappeared during the stationary phase. In cultures switched from sulfur to iron medium, there was a correlation between iron oxidation and the rusticyanin level. In sulfur cultures inoculated with stationary growing sulfur cells, rusticyanin synthesis de novo was observed. Our data agree with a control on rusticyanin level in the cells depending on the electron donor present in the medium, and on the growth phase in sulfur-grown cells. Furthermore, they are consistent with the involvement of rusticyanin in iron oxidation and suggest that this protein could play also a role in sulfur-grown cells.