Metal sulfide formation in the human intestine

The geochemical importance of dissimilatory sulfate reduction in the formation of diagenetic iron sulfides in sedimentary environments is generally accepted. The environmentally important sulfate-reducing prokaryotes (SRP) are also recognized to be normal constituents of gut microbiota in humans and animals. Some potentially adverse health implications of sulfidogenic bacteria are attributed to the cytotoxic effect of hydrogen sulphide. Several reports suggest that SRP activity in the large intestine may be implicated in inflammatory bowel disease and ulcerative colitis. Sulfidogenic anaerobes have also been postulated as aetiological agents in a number of diseases such as cholecystitis, brain and abdominal abscesses, rheumatic disease, and bacteraemia.

Little attention has been paid to the possible effects of metal sulfide formation by SRP inhabiting the large intestine. We consider two plausible mechanisms for SRP impact on human health via the formation of sulfides. (I) SRP may substantially reduce the bioavailability of essential metals, such as iron and copper, by precipitating them in the form of insoluble sulfides; (II) SRP can produce potentially harmful nano-crystals of metal sulfide.

A new anaerobic spore-forming sulfidogenic Firmicute was isolated from human faeces.