Metabolic Pathway of Microorganisms - Oxydation of Sulfur Compounds

3 important questions on Metabolic Pathway of Microorganisms - Oxydation of Sulfur Compounds

What are the most common sulfur compounds used as electron donors and what is the result of sulfur chemolithotrophy?

H2S, S0, and S2O32-; SO32- can also be oxidized. Elemental sulfur exists as a potential energy reserve through the oxidation of sulfur to sulfate. The result is that many sulfur bacteria have evolved to be acidtolerant.

What is the Sox system and how does it work?

A pathway for conserving energy from the oxidation of sulfur compounds. There are four key proteins: SoxXA, SoxYZ, SoxB, and SoxCD, which are all present in the periplasm. SoxXA forms a bond between the sulfur compound and SoxYZ. The compund is released as sulfate through SoxB. SoxCD mediates the removal of 6 electrons from the compound.

What happens in microbes if the protein SoxCD is missing from the Sox system?

Sulfur bound to SoxYZ is added to a growing sulfur granule in the periplasm, which is transported to the ceriplasm where it is oxidized to SO32-. This compound is oxidized to sulfate plus two electrons through either sulfite reductase or adenosine phosposulfate reductase. This oxidation yields an energy-rich phosphate bond.

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