Sulfur/sulfide oxidizing bacteria

Sulfur/sulfide oxidizing bacteria (e g., Thiobacillus) Aerobic Oxidize sulfide (S2-) to elemental sulfur (S), sulfide to sulfate (SO4 ), or sulfur to sulfate. Strains that produce sulfate (e g., Thiobacillus) create sulfuric acid (H2S04) H+ (lower pH)... 

Sulfur/Sulfide Oxidizing Bacteria This broad family of aerobic bacteria derives energy from the oxidation of sulfide or elemental sulfur to sulfate (Fig. 10.10). Some types of aerobes can oxidize sulfur to sulfuric acid, with pH values as low as one reported. These Thiobacillus strains are most commonly found in mineral deposits, and are largely responsible for acid mine drainage, which has become an environmental concern. They proliferate inside sewer lines and can cause rapid deterioration of concrete mains and the reinforcing steel therein. 

Sulfur-sulfide-oxidizing bacteria. This broad family of aerobic bacteria derives energy from the oxidation of sulfide or elemental sulfur to sul-... 

Elemental sulfur is an oxidation product of dissolved sulfide. It may form inorganically, but in near-surface marine sediments where dissolved sulfide exists close to the sediment-water interface, it commonly forms because of the metabolic activities of sulfide oxidizing bacteria. Bacterial mats of filamentous sulfur producing Beggiatoa spp. have been observed in the surface of nearshore marine sediments (Schimmelmann and Kastner, 1993 Troelsen and Jorgensen, 1982). Elemental sulfur can be stored within invaginations of the bacterial cell wall in the form... 

In natural ecosystems the sulfur cycle should be in balance, meaning that the amount of sulfide that is oxidized should correspond to the amount of sulfate that is reduced. Such a balance can be found in a sulfuretum . This is a syntrophical community of bacteria in which H2S produced by sulfate reducing bacteria is reoxidized by the sulfur compound oxidizing bacteria. 

Apart from the above sulfide oxidation reactions, other sulfur compounds, such as sulfur and thiosulfate, can be oxidized by sulfur compound oxidizers. Furthermore, nitrate can be used as oxidant instead of oxygen. In Table 2 a list is shown of some other sulfur compound oxidation reactions occurring in chemotrophic sulfur compound oxidizing bacteria. It should be... 

Elemental sulfur is often observed as an intermediate product in the oxidation of sulfide to sulfate in sulfur compound oxidizing bacteria. It can be present in considerable concentrations but will eventually be further oxidized to sulfate. The elemental sulfur is stored in sulfur globules, which some bacteria deposit inside the cell membrane and others outside the cell membrane. Later in this chapter the properties of these sulfur globules are discussed. 

In chemical oxidation reactions, the first oxidation step (forming of sulfide radicals) is catalyzed by metal-ions like Fe, and Cu. In most sulfur compound oxidizing bacteria, the first step in the oxidation of sulfide to sulfur is catalyzed by the enzyme flavocytochrome c [3]. In a number of bacteria with the capacity to oxidize sulfide to sulfur, flavocytochrome c has not been found and other cytochromes or quinones are believed to catalyze the oxidation of sulfide in these organisms. 

Sulfiir/sulfide-oxidizing bacteria are aerobic and oxidize sulfide to el-emental sulfur (S2 — S + 2e), sulfide to sulfate... 

As just noted, aerobic sulfide-oxidizing bacteria use sulfides to produce sulfates, whereas anaerobic SRB utilize sulfates to produce sulfides. The two types of bacteria often are found in the same biofilm, at different locations (aerobic versus anaerobic), with both participating in this synergistic sulfur cycle. 

The scrubbing liquid, containing sulfide, is directed to the bioreactor where the sulfide is oxidized into elemental sulfur by autotrophic sulfide-oxidizing bacteria such as Thioalcalovibrio and Thioalcalobacterium as follows ... 

Thiobacillus thiooxidans is an aerobic organism that oxidizes various sulfur-containing compounds to form sulfuric acid. These bacteria are sometimes found near the tops of tubercles (see Chap. 3, Tubercu-lation ). There is a symbiotic relationship between Thiobacillus and sulfate reducers Thiobacillus oxidizes sulfide to sulfate, whereas the sulfate reducers convert sulfide to sulfate. It is unclear to what extent Thiobacillus directly influences corrosion processes inside tubercles. It is more likely that they indirectly increase corrosion by accelerating sulfate-reducer activity deep in the tubercles. 

A special case represents acid sulfate waters released from mines where metal sulfide ores and lignite have been exploited. S- and 0-isotope data may define the conditions and processes of pyrite oxidation, such as the presence or absence of dissolved oxygen and the role of sulfur-oxidizing bacteria (i.e. Taylor and Wheeler 1994). 

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