Molecular Characterization of Copper and Cadmium Resistance Determinants in the Biomining Thermoacidophilic ArchaeonSulfolobus metallicus

Abstract

Sulfolobus metallicus is 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 in S. metallicus remain uncharacterized. Proteomic analysis of S. metallicus cells 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 in S. metallicus treated in the presence of 1 mM Cd suggesting that at least in part, a common general response to these two heavy metals. The S. metallicus genome contained two complete cop gene clusters, each encoding a metallochaperone (CopM), a Cu-exporting ATPase (CopA), and a transcriptional regulator (CopT). Transcriptional expression analysis revealed that copM and copA from each cop gene cluster were cotranscribed and their transcript levels increased when S. metallicus was 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 the cop gene cluster in Archaea and characterizes some of the Cu and Cd resistance determinants in a thermophilic archaeon employed for industrial biomining.

Heavy Metal Resistance Strategies of Acidophilic Bacteria and Their Acquisition: Importance for Biomining and Bioremediation

“…In this way, the reserve polyP would also be supplying energy to the metal detoxifying systems. A similar mechanism may also exist in Sulfolobales (Orell et al, 2010;Orell et al, 2012;Orell et al, 2013). Although the proposed mechanism for metal resistance needs to be proven, it may be eventually functional in all polyP-accumulating biomining microorganisms (Orell et al, 2010) (see Fig.…”

“…In the environment of biomining microorganisms, copper and other nominal metal concentrations are one or two orders of magnitude greater than those tolerated by neutrophiles (Remonsellez et al, 2006;Orell et al, 2010;Orell et al, 2013). However, since the growth conditions of these two types of bacteria are completely diff erent the comparison cannot be directly made.…”

Transcriptomes of the Extremely Thermoacidophilic Archaeon Metallosphaera sedula Exposed to Metal “Shock” Reveal Generic and Specific Metal Responses

“…Both candidate homologs in M. sedula (Msed_1675 and Msed_1674) of two cysteine biosynthesis enzymes in M. maripaludis were upregulated by HD Cu 2ϩ (74). The upregulation of a S. metallicus homolog of Msed_1675 was observed in a proteomic study of Cu and Cd challenge (13). Downregulation of L-glutamine and L-arginine biosynthesis was also observed and would prevent the diversion of L-glutamate away from L-cysteine biosynthesis (75).…”

“…Resistance to copper in extreme thermoacidophiles is mediated at least by mechanisms involving active transport and metal sequestration (7,(10)(11)(12)(13)(14)(15). Single-unit, membrane class 1B metal-translocating P-type ATPases are implicated in homeostasis and resistance to Cu 2ϩ and Cu ϩ , as well as to Ag ϩ , Pb 2ϩ , Zn 2ϩ , Cd 2ϩ , and Co 2ϩ (16).…”

“…Other archaeal acidophiles also contain versions of the cop operon. The Sulfolobus metallicus genome contains duplicate versions of the copTMA operon, making it unique among known thermoacidophilic archaea (13). The genome of Ferroplasma acidarmanus contains a cop operon (copYZB) with a structure and a response to copper similar to those of copRTA (10).…”