The thiosulfate-oxidizing pathway is a metabolic pathway used by some sulfur lithotrophs to oxidize thiosulfate (S2O3 2-) as an energy source. This pathway is found in bacteria such as Thiobacillus spp. and is an important process in the sulfur cycle of the environment.
The thiosulfate-oxidizing pathway involves several steps:
- Thiosulfate uptake: Thiosulfate is transported into the cell by a transporter protein.
- Thiosulfate hydrolysis: Thiosulfate is hydrolyzed by the enzyme thiosulfate hydrolase to form sulfite (SO3 2-) and elemental sulfur (S).
- Sulfur oxidation: Elemental sulfur is oxidized by the enzyme sulfur oxygenase reductase (SOR) to form sulfite.
- Sulfite oxidation: Sulfite is further oxidized to sulfate (SO4 2-) by the enzyme sulfite oxidase.
The electrons released from the oxidation of thiosulfate are transferred to the electron transport chain, generating a proton motive force that can be used to synthesize ATP via oxidative phosphorylation.
Overall, the thiosulfate-oxidizing pathway allows sulfur lithotrophs to use thiosulfate as an energy source and play an important role in the biogeochemical cycling of sulfur in the environment. The pathway also produces sulfate, which can be used as a terminal electron acceptor in the anaerobic respiration of some bacteria.