Microbial thiosulphate reaction arrays: the interactive roles of Fe(III), O₂ and microbial strain on disproportionation and oxidation pathways

Abstract

In this work, we experimentally evaluate pH and SO4(2-) dynamics associated with abiotic and microbial S2O3(2-) oxidation under varying [O2], [Fe(III)] and microbial strain/consortia (two pure strains, Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, their consortia, and two enrichments from an acidic environmental system, Moose Lake 2002 and Moose Lake 2003). Results of the batch experiments demonstrate highly active microbial processing of S2O3(2-) while abiotic controls under identical experimental conditions remain static with no pH decrease. When abiotic controls were manually titrated with acid to achieve similar pH decreases to those occurring in the microbial treatments, different S pathways were involved. In particular, disproportionation is a substantial component of initial microbial S2O3(2-) processing, and is accelerated by the presence of Fe(III), indicating that recycling of S through intermediate oxidation states is likely to be widespread in acidic mine environments where high [Fe(III)] is common. Furthermore, the microbially mediated S reaction pathways were dependent on both environmental conditions and microbial strain/consortia, indicating that microbial community structure also plays a key role. Collectively, these results highlight the importance of microbial activity, their poor representation by abiotic S models, the likelihood that Fe(III), rather than O2, is a key control on microbial S processing in acid environments and the need to identify the microbial community/strain involved.

The Importance of Thiosalts Speciation: Review of Analytical Methods, Kinetics, and Treatment

“…For example, Thiobacilus ferroxidans yields thiosulfate and tetrathionate; T. tepidarius yields diothionate and T. versutus oxidizes thiosulfate without intermediates and accumulate sulfur (Wentzien et al, 1994). In some cases, the bacteria population will influence the final product of the reaction; however, these final products will also be determined by the conditions of the solution (Warren et al, 2008;Wentzien et al, 1994).…”

“…Under acidic conditions, thiosalts will be susceptible to disproportionation, meaning that the compounds will oxidize regardless of the microbial activity. Warren et al (2008) identified disproportionation as important for the initial microbial processing of thiosulfate. At basic conditions, the most likely mechanism is that microorganisms change the oxidation state of sulfur oxidizing thiosulfate to tetrathionate and then to sulfate as reported in reaction 7 (Sorokin and Tourova, 2005).…”

Microbial behaviour under conditions relevant to heap leaching: Studies using the sulfur-oxidising, moderate thermophile Acidithiobacillus caldus

“…In the present study it was found that thiosulfate was a short-lived intermediate during tetrathionate oxidation to sulfate. Warren et al (2008) examined thiosulfate oxidation using At. thiooxidans and At.…”

Implications of Microbial Thiosulfate Utilization in Red Clay Sediments of the Central Indian Basin: The Martian Analogy

“…Microbially reversible reduction of Fe (III) to Fe (II; Pentrakova et al, ) also controls S‐disproportionation in clay minerals. At near‐neutral or high pH, Fe 3+ reduction induces S‐disproportionation unlike total oxidation to SO 4 2− and H + at low pH and forms polythionates or elemental S°(Warren et al, ) with precipitation of goethite (FeOOH). Many of these features are evident in the CIB red clay (Nath et al, ; Mascarenhas‐Pereira & Nath, ) and are proxies indicative of S‐disproportionation.…”