Bacteria sulfide oxidation

Yagi laid the foundation for the enzymology of CODH when he discovered an enzymatic activity in sulfate-reducing bacteria that oxidizes CO to CO2 (118). Twenty-five years later, the first CODH was purified to homogeneity (119, 120). The homogeneous C. thermo-aceticum CODH was shown to contain 2 mol of nickel, 12 iron, 1 zinc, and 14 acid-labile inorganic sulfide per afS dimeric unit (120). 

Cork [283], Sublette [284], and others have identified a number of chemolithotrophic bacteria which oxidize elemental sulfur and use reduced or partially reduced sulfur compounds as an energy source, in the presence of various carbon sources (such as carbon dioxide or bicarbonate) and reduced nitrogen (e.g., ammonium ion). In the case of Cork et al. s work, the anaerobic photosynthetic bacterium Chlorobium thiosulfatophilum is used to convert sulfides to sulfate. The economics of this process was not favorable due to the requirement of light for the growth of the bacterium. 

This reaction is mediated by bacteria called sulfide oxidizers. 

In high-temperature hydrothermal systems, sulfide-oxidizing bacteria are responsible for most of the primary production supporting the vent community. As shown in Eq. 19.7,... 

Minerals, in the body, 36 24 Mineral sulfide-oxidizing acidophilic bacteria, 36 106-123... 

Organisms such as Thiobacillus thiooxidans and Clostridium species have been linked to accelerated corrosion of mild steel. Aerobic Thiobacillus oxidizes various sulfur-containing compounds such as sulfides to sulfates. This process promotes a symbiotic relationship between Thiobacillus and sulfate-reducing bacteria. Also, Thiobacillus produces sulfuric acid as a metabolic by-product of sulfide oxidation. 

Since the reduction potential for the Fe(II) / Fe(III) couple is + 0.77 V at pH 7, the energy obtainable in this reaction is small. These bacteria always oxidize reduced sulfur compounds, too. Especially interesting is their oxidation of pyrite, ferrous sulfide (Eq. 18-24). The Gibbs energy change was calculated from published data325 using a value of Gf° for Fe (OH)3 of... 

Measured rates of microbial oxidation of sulfide in lakes range from 0 to over 100,000 mmol/m2 per year (Table IV). These rates, which are comparable to measured rates of sulfate reduction (Table I), suggest that microbial oxidation of sulfide is capable of supplying sulfate at rates needed to sustain sulfate reduction. The majority of measurements are for photosynthetic bacteria in the water column. Symbiotic sulfate reduction and sulfide oxidation are known to occur and lead to dynamic cycling of S within anaerobic water... 

The Rio Pilcomayo is a major river that originates in Bolivia and forms part of the boundary between Paraguay and Argentina. The water and sediments in the river are substantially contaminated with arsenic from the Potosi mines in Bolivia (Hudson-Edwards et al., 2001), 245. The arsenic content of Rio Pilcomayo actually increases from 65 pg L-1 at 10.2km downstream from the mines to 100 pg L-1 at about 151 km downstream (Hudson-Edwards et al., 2001), 240, 244. The arsenic increase may be due to a decrease in pH (from 10.3 to 8.42), increased oxidation of the river sediment, and increased activity of sulfide-oxidizing bacteria (Hudson-Edwards et al., 2001), 244-245. 

The capacity of chemoautotrophic bacteria to oxidize hydrogen sulfide as a source of energy for CO2 fixation is well known (20). However, the realization that entire bacterial and invertebrate communities can be fueled by... 

Sulfide oxidation by phototrophic bacteria is catalyzed by c-type cytochromes, flavocytochromes and even cytochrome c complexes (see 4.2). A heat-labile cytochrome c-550 of Thiocapsa roseopersicina is responsible for the oxidation of sulfide. The end product is elemental sulfur and it is assumed that this cytochrome might also catalyze the reverse reaction by reducing the intracellularly stored elemental sulfur to sulfide (4.9V... 

Elemental sulfur was also formed during sulfide oxidation by a cytochrome c-flavocytochrome c-552 complex in Chromatium vinosum (42). Flavocytochromes of different phototrophic bacteria act as sulfide cytochrome c reductases and there was one report that a flavocytochrome possessed even elemental sulfur reductase activity (see 4.9V All flavocytochromes examined so far are heat-labile and are reduced by sulfide forming thiosulfate under strictly anaerobic conditions (4.9V The small acidic cytochromes c-551 of Ectothiorhodospira halochloris and Ectothiorhodospira abdelmalekii. both located on the outside of the cell membrane, stimulated the velocity of sulfide... 

Some microbes can produce organic acids, such as formic and succinic, or mineral acids such as sulfuric acid. Some bacteria can oxidize sulfur or sulfide to sulfate or reduce sulfates, very often to hydrogen sulfide as end product. (Dexter)14... 

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