Sulfur Cycling and the Intestinal Microbiome

Area of Science:

• Microbiology
• Gut Microbiome
• Sulfur Metabolism

Background:

• The gut harbors an anaerobic sulfur cycle crucial for hydrogen sulfide (H2S) production.
• Sulfate-reducing bacteria (SRB) are primary H2S producers, but heterotrophic bacteria also contribute via cysteine desulfhydration.
• Dietary components fuel bacterial fermentation, producing molecular hydrogen that supports SRB dominance.

Purpose of the Study:

• To review the anaerobic sulfur cycle in the gut.
• To elucidate the mechanisms of hydrogen sulfide production in the intestinal environment.
• To discuss the dual role of hydrogen sulfide in the gut ecosystem.

Main Methods:

• Literature review of anaerobic gut microbiology and sulfur metabolism.
• Analysis of bacterial respiration pathways and electron donors/acceptors.
• Examination of dietary influences on microbial fermentation and H2S production.

Main Results:

• Hydrogen sulfide is produced by both sulfate-reducing bacteria and heterotrophic bacteria in the gut.
• Molecular hydrogen and lactate serve as electron donors for SRB, with sulfate as the terminal electron acceptor.
• Dietary fiber degradation fuels bacterial fermentation, promoting H2S production.

Conclusions:

• Hydrogen sulfide production in the gut is a complex process involving multiple bacterial groups and dietary substrates.
• While H2S can offer benefits to gut bacteria, elevated levels pose a toxicity risk to the host.
• Understanding these dynamics is key to managing gut health and microbial balance.