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. Author manuscript; available in PMC: 2017 Jul 1.
Published in final edited form as: Mol Microbiol. 2016 May 2;101(1):62–77. doi: 10.1111/mmi.13372

Figure 9. Sulfide physiology in E. coli.

Figure 9

Excessive import of cystine by TcyP enlarges cysteine pools. Most cysteine is excreted, but some is adventitiously degraded by tryptophanase and other enzymes. The sulfide is membrane permeant and accumulates in the local environment. Environmental sulfide also arises from sulfate-reducing bacteria in nearby anoxic zones. Intracellular sulfide inhibits the proton-pumping cytochrome bo oxidase, diverting respiratory flux through the non-pumping cytochrome bd oxidase.