Molecular Characterization of Copper and Cadmium Resistance Determinants in the Biomining Thermoacidophilic ArchaeonSulfolobus metallicus
Sulfolobus metallicusis a thermoacidophilic crenarchaeon used in high-temperature bioleaching processes that is able to grow under stressing conditions such as high concentrations of heavy metals. Nevertheless, the genetic and biochemical mechanisms responsible for heavy metal resistance inS. metallicusremain uncharacterized. Proteomic analysis ofS. metallicuscells exposed to 100 mM Cu revealed that 18 out of 30 upregulated proteins are related to the production and conversion of energy, amino acids biosynthesis, and stress responses. Ten of these last proteins were also up-regulated inS. metallicustreated in the presence of 1 mM Cd suggesting that at least in part, a common general response to these two heavy metals. TheS. metallicusgenome contained two completecopgene clusters, each encoding a metallochaperone (CopM), a Cu-exporting ATPase (CopA), and a transcriptional regulator (CopT). Transcriptional expression analysis revealed thatcopMandcopAfrom eachcopgene cluster were cotranscribed and their transcript levels increased whenS. metallicuswas grown either in the presence of Cu or using chalcopyrite (CuFeS2) as oxidizable substrate. This study shows for the first time the presence of a duplicated version of thecopgene cluster inArchaeaand characterizes some of the Cu and Cd resistance determinants in a thermophilic archaeon employed for industrial biomining.