Abstract
Redox-related gaseous molecular species in the gastrointestinal tract are derived from the chemical oxidation-reduction reactions, enzymatic reactions, swallowing, and bacterial production. Recent studies have demonstrated the crucial roles of the microbiota and gaseous molecules in the pathogenesis of gastrointestinal inflammatory and functional diseases. Especially in the hypoxic condition of the large intestine, various bacteria produce acetic acid, methane, and hydrogen sulfide using hydrogen molecules generated by the fermentation reaction as an energy source. In this review, we summarized the recent advances in the biology of redox-related gaseous molecules in the gastrointestinal tract.