Sulfur-oxidizing bacteria examples

For some bacterial species other than SRB, it has been shown that there is a positive correlation between their numbers and the severity of corrosion as measured by corrosion rates For example, it has been reported " that the abundance of sulfur-oxidizing bacteria (SOB) had been correlated positively with corrosion. However, when it comes to SRB, there is evidence to believe that no relationship exists between the corrosion rate and the number of the bacteria cells. ... 

S in the atmosphere which is present as SO2, H2S, and organic sulfur (DMS, (013)28, CS2, COS etc.) oxidizes easily and removes by rainfall, implying that residence time of sulfur in the atmosphere is short. Activities of microorganism takes important role for short-term sulfur cycle. For example, DMS that is produced by plankton transfers from ocean to atmosphere (Lovelock et al. 1972). This sulfur flux is estimated as (1.9-0.6) x 10 mol year (4 2 x 10 g year ). Activities of bacteria promote oxidation-reductiOTi reactimis in soils and affect the rate of sulfur transfer between soils and soil water. For example, sulfate-reducing bacteria and sulfur-oxidizing bacteria promote the following reactions. 

The natural sulfur cycle involves many sulfur-reducing and sulfur-oxidizing bacteria. For example, is oxidized to elemental sulfur and to [804] , and the reverse processes convert mobile [804] to immobilized S. (a) At the end of the sulfur-reduction sequence, HS may be produced instead of 8. What influences this outcome, and what... 

Sulfur-oxidizing bacteria (SOB) Aerobic, acidic Oxidize sulfur and sulfide to form Sulfuric acid Thiobacillus genus is a common example... 

Rusticyanin is found in Thiobacillus ferrooxidans, an acidophilic, chemolithotrophic sulfur bacterium utilizing Fe + and reduced sulfur compounds as its sole energy source. T. ferrooxidans does not produce rusticyanin when grown on reduced sulfur. Similar to other substrate-inducible cupredoxms, the msticyanin gene is activated when soluble iron is present in the media. Little is known about its redox partners and it should be noted that rusticyanin itself does not carry out Fe + oxidation. Other iron-oxidizing bacteria, for example, Leptospirillum ferrooxidans, prodnce a cytochrome which substitutes rusticyanin functionally. To date T. ferrooxidans remains the only source for rusticyanin. 

Hydrogen sulfide can be oxidised to elemental sulfur, for example, by green and purple sulfur bacteria. Further oxidation of elemental sulfur by sulfur oxidising bacteria can produce sulfate. 

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). 

Disproportionation reactions do not cause a net oxidation of the sulfur species, yet they have a key function in sulfide oxidation. Disproportionation provides a shunt in the sulfur cycle whereby the H S formed by this reaction may be oxidized again to the same sulfur intermediate by metal oxides. Manganese oxide, for example, rapidly oxidizes H S to S without participation of bacteria, but does not oxidize the S further to sulfate (Burdige 1993). The elemental sulfur may, however, be disproportionated (Eq. 8.19) whereby a fourth of it is oxidized completely to sulfate while the remaining three fourths return to the sulfide pool. Through repeated partial oxidation of sulfide to elemental sulfur with manganese oxide and subsequent disproportionation of the elemental sulfur to sulfate and sulfide a complete oxidation of sulfide to sulfate by manganese oxide may be achieved (Fig. 8.16 Thamdrup et al. 1993 Bdttcher and Thamdmp 2001) ... 

Iron-oxidizing bacteria (lOB) Acidic, aerobic Oxidize ferrous ions to ferric ions Sulfuric acid, iron sulfate Thiobacillus ferrooxidans is a well-known example... 

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