Abstract
We report the application of confocal laser scanning microscopy CLSM and Raman spectroscopy on the (bio)chemical oxidation of pyrite and chalcopyrite, in order to understand how surface sulfur species () affects biofilm evolution during mineral colonization by Acidithiobacillus thiooxidans. We found that cells attachment occurs as cells clusters and monolayered biofilms within the first 12 h. Longer times resulted in the formation of micro- and macrocolonies with variable cell density and higher epifluorescence signal of the extracellular polymeric substances (EPS), indicating double dynamic activity of A. thiooxidans: sulfur biooxidation and biofilm formation. Raman spectra indicated consumption modification during biofilm evolution. Hence, cell density increase was primarily associated with the presence of ; the presence of refractory sulfur species on the mineral surfaces does not to affect biofilm evolution. The EPS of the biofilms was mainly composed of extracellular hydrophobic compounds (vr. gr. lipids) and a minor content of hydrophilic exopolysaccharides, suggesting a hydrophobic interaction between attached cells and the altered pyrite and chalcopyrite.
Highlights
Sulfide minerals (SMs) are the main source of base metals (e.g., Fe, Ni, Cu, Zn, and Pb) in the world
We report the application of confocal laser scanning microscopy CLSM and Raman spectroscopy on thechemical oxidation of pyrite and chalcopyrite, in order to understand how surface sulfur species (Sn2−/S0) affects biofilm evolution during mineral colonization by Acidithiobacillus thiooxidans
At 120 h, in the eMPE, CLSM analysis confirmed the progressive senescence of biofilms on the surface, and only dispersed attached cells were observed (Figure 1(d)); a multilayered biofilm was observed in the eMCE, which was mainly composed by extracellular hydrophobic compounds vr. gr. lipids (Figure 1(h), Table 1)
Summary
Sulfide minerals (SMs) are the main source of base metals (e.g., Fe, Ni, Cu, Zn, and Pb) in the world. Pyrite is acid insoluble, as Fe3+ is its main oxidizing agent at high and low pH, as it has been described by Sand et al [1] and Schippers and Sand [2]. These authors concluded in these reports that the mechanism and chemistry of SM oxidation are determined by such electronic structure as well as the acid solubility. The oxidation of an acid insoluble SM proceeds via the thiosulfate mechanism by means of electron extraction, by the indirect attack of hydrated Fe(III) ions. The S0 is a byproduct produced in significant amounts (10–20%) during the chemical or electrochemical oxidation of pyrite at pH < 2, moderate temperature and pressure, and in the absence of microorganisms [2,3,4,5]
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