The Study On The Speciation And Transformation Of Elemental Sulfur Mediated By Thermophile Sulfolobus Metallicus

This work mainly focused on the sulfur speciation and its transformation mediated by extreme thermophile S. metallicus during the oxidation of elemental sulfur; the surface sulfur speciation and its transformation on pyrite and chalcopyrite during leaching process in the presence of S. metallicus; The differential expression of sulfur oxidation gene sor in S. metallicus grown on different substrate, which provided some basic data to illustrate the biological oxidation process of inorganic sulfur compounds and the mechanism of bioleaching in extreme thermophilic leaching system. The primary subjects include four parts as follows:(1) Investigation of sulfur speciation transformation during the elemental sulfur oxidation by S. metallicusThe sulfur speciation transformation during the elemental sulfur oxidation by S. metallicus was investigated by FT-IR and Sulfur K-edge X-ray Absorption Near Edge Structure (XANES). The FT-IR result showed the surface protein expression of S. metallicus grown on elemental sulfur was obviously upregulated. XANES analysis showed that the-SH group content of bacteria was also obviously increased; the fitted XANES result indicated that 28.4% of elemental sulfur have converted to polymeric form. These result indicated that the protein rich in-SH group participated in the activation-oxidation process of elemental sulfur, and provided proof for the validity of the sulfur activation model in thermophile.(2) The surface sulfur speciation and its transformation on pyrite during leaching process in the presence of S.metallicusSulfur speciation on the surface of pyrite leached by extreme thermophile S. metallicus was investigated by using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and sulfur K-edge XANES. As the result, jarosite, elemental sulfur, thiosulfate and/or thiosulfate-like species were found. Among these compounds elemental sulfur was the composition of sulfur-rich layer. The leaching results indicate the oxidantion of pyrite by S. metallicus was effective, and the passivation effect of jarosite as well as elemental sulfur was impaired. In addition, thiosulfate found in this study provided novel evidence for surface-bound thiosulfate involved in the stepwise oxidation of pyrite by the extreme thermophile S. metallicus.(3) The surface sulfur speciation and its transformation on chalcopyrite during leaching process in the presence of S. metallicusSulfur speciation on the surface of chalcopyrite leached by extreme thermophile S. metallicus was investigated by using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and sulfur K-edge XANES. The results showed that there was an optimum range of the redox potential for chalcopyrite dissolution, a redox potential above a threshold will restrain the dissolution of chalcopyrite. The fitted results of XANES spectra indicated that covelline would occur in the leaching system when redox potential was below a critical value, which might account for the high leaching rate. In addition, results showed the jarosite would accumulate during leaching process, which was the main factor of passivation, while the pasivation effect of elemental sulfur was relatively weak in the presence of S. metallicus.(4) The differential expression of sor in S. metallicus grown on different substrateReal-time PCR was used to investigate the differential expression of sor in S. metallicus grown on different substrate. The results showed that comparing to S. metallicus grown on ferrous substrate, the expressions of sor of S. metallicus grown on reduced inorganic sulfur compounds were obviously upregulated. Specifically, The expression of sor in elemental sulfur cultured S. metallicus was 65 times as much as it grown in ferrous sulfate, while the upregulations of expression in pyrite and chalcopyrite were less obvious, which are 7.5 and 9.1 times, respectively. These results indicate that regulation of sor of S. metallicus is substrate-depended, and provide proof of the production of elemental sulfur during the dissolution of metal sulfide on the molecular level.