Exploring reaction mechanisms of dissimilatory ferric reduction-coupled sulfur oxidation (DIRSO) by acidophilic prokaryotes and its relevance for bioleaching and acid mine drainage formation
Analytical Chemistry
Mineralogy, Petrology and Geochemistry
Final Report Abstract
Bioleaching processes and acid mine drainage (AMD) generation are mainly driven by microbial aerobic iron(II) and sulfur oxidation, and they are also greatly influenced by microbial dissimilatory iron(III) reduction coupled to sulfur oxidation (DIRSO) which has been described for anaerobic conditions at low pH for acidophiles, but iron reduction was observed under aerobic conditions as well. The research project explored the physiology and reaction mechanisms of iron(III) reduction coupled to sulfur compound oxidation by pure cultures of acidophilic archaea and bacteria. Cell-specific iron(III) reduction rates for different Acidithiobacillus (At.) strains during batch culture growth or stationary phase with iron(III) (~40 mM) as electron acceptor and elemental sulfur or tetrathionate as electron donor (1% or 5 mM, respectively) were determined. The rates were highest under anaerobic conditions for the At. ferrooxidans type strain with 6.8 x 10^6 and 1.1 x 10^7 reduced iron(III) ions per second per cell for growth on elemental sulfur and tetrathionate, respectively. The iron(III) reduction rates were somehow lower for the anaerobically sulfur grown archaeon Ferroplasma acidiphilum, and lowest for the sulfur grown At. caldus type strain under aerobic conditions (1.7 x 10^6 and 7.3 x 10^4 reduced iron(III) ions per second per cell, respectively). The rates for five strains of At. thiooxidans (aerob) were in between those for At. ferrooxidans (anaerob) and At. caldus (aerob). Thiosulfate as sulfur intermediate was found for At. ferrooxidans during anaerobic growths on tetrathionate and iron(III), and a small concentration was measured during aerobic growths on tetrathionate without iron(III). For the At. thiooxidans type strain thiosulfate was found with tetrathionate grown cells under aerobic conditions in presence and absence of iron(III). Evidence for hydrogen sulfide production at low pH was found for the At. ferrooxidans as well as the At. thiooxidans type strains during microaerophilic growth on elemental sulfur and for At. ferrooxidans during anaerobic growths on tetrathionate and iron(III). The occurrence of sulfur compound intermediates supports the hypothesis that chemical reduction of iron(III) ions takes place by sulfur compounds released by the microbial cells. In search of novel acidophilic bacteria a mixotrophic and acidophilic bacterial strain BGR 140T was isolated from mine tailings in the Harz Mountains near Goslar, Germany. BGR 140T grew aerobically at 25– 55 °C (optimum 45 °C) and at pH 1.5–5.0 (optimum pH 3.0). The strain grew also facultative anaerobe, was capable of anaerobic growth with iron(III) as an electron acceptor. The results of further analysis showed that strain BGR 140T (=DSM 109850T=JCM 39070T) represents a novel species of the genus Sulfobacillus, for which the name Sulfobacillus harzensis sp. nov. was proposed and accepted.
Publications
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Sulfobacillus harzensis sp. nov., an acidophilic bacterium inhabiting mine tailings from a polymetallic mine. International Journal of Systematic and Evolutionary Microbiology, 71(7).
Zhang, Ruiyong; Hedrich, Sabrina; Jin, Decai; Breuker, Anja & Schippers, Axel
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Sulfur intermediates and rates of ferric reduction coupled to sulfur oxidation by Acidithiobacillus species. Abstract and Poster at the 24th International Biohydrometallurgy Symposium (IBS), 20 – 23 November 2022
Breuker, A. & A. Schippers
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Rates of iron(III) reduction coupled to elemental sulfur or tetrathionate oxidation by acidophilic microorganisms and detection of sulfur intermediates. Research in Microbiology, 175(1-2), 104110.
Breuker, Anja & Schippers, Axel
