Sulfur: abiotic oxidation oxidizing bacteria

Oxidation of reduced sulfur species. Oxidation of reduced sulfur species in the presence of oxygen can occur spontaneously, without bacterial mediation. Bacteria of the family Thiobacteriaceae are probably the most important bacteria involved in sulfur oxidation. Of these, bacteria of the genus Thiobacillus have been most studied (Goldhaber and Kaplan 1974 Cullimore 1991). The first product of sulfide oxidation abiotically or by Thiobaccillus is thought to be elemental sulfur according to... 

The role of sulfur- and iron-oxidizing bacteria. As already noted, the rates of FeS2 and Fe(II) oxidation in environmental systems often differ substantially from the abiotic rates. Usually natural rates are much faster than laboratory abiotic rates. The reasons include inorganic catalysis and especially enzymatic oxidation by microorganisms. Oxidation of Fe(ll), for example, is catalyzed by some clays and metals, including Al, Fe, Co +, Cu, and Mn, and also HPO (Stumm and Morgan 1981). 

In the presence of oxygen, abiotic oxidation of hydrogen sulfide can occur. However, this reaction can be catalyzed by sulfur-oxidizing bacteria (Figures 11.15 and 11.16). Oxidation of reduced sulfur occurs at interfaces the oxic-anoxic interface for abiotic and chemolithotrophic oxidation and, in the anoxic zone, the light-dark interface for phototrophic oxidation. 

Figure 8.20. Simplified scheme for the oxidation of H2S by O2 mediated by a variety of bacteria. The gradient zone between O2 and H2S is the environment of many colorless sulfur bacteria, among which the type Beggiatoa often reach high population densities and form white mats on the mud or sediment-water interface. If light penetrates at the zonation between O2 and H2S, phototrophic, often colorful, sulfur bacteria grow. Reduced sulfur can also be oxidized abiotically, for example, by Fe(III)(hydr)oxides or even by O2 in the presence of metal-ion catalysts.

Sulfur and oxygen isotopes. Stable sulfur and oxygen isotopes can provide clues regarding the relative importances of O2 versus Fe(III) oxidation of pyrite, and whether the oxidation is abiotic (sterile) or involves bacteria (Taylor et al. 1984a, 1984b). The isotopic data are reported in S (per mil or %o) units, where... 

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