70% of Gut Bacteria Can Process Hydrogen Gas in Human Colon
- Authors
- Patricia G. Wolf, Ambarish Biswas, Sergio E. Morales, Chris Greening, H. Rex Gaskins
- Journal
- Gut Microbes
- Year
- 2016
- DOI
- 10.1080/19490976.2016.1182288
- Study Type
- clinical
- Peer Reviewed
- Yes
- Country
- United States
- Health Condition
- Digestive Disorders
- Body System
- Digestive
TL;DR
Most of the helpful bacteria living in your gut can process a gas called hydrogen that gets made when you digest food, and scientists just figured out exactly how they do it—which could help us better understand how your gut stays healthy.
Key Finding
Approximately 70% of human colonic microbes possess the genetic capacity to metabolize molecular hydrogen, with electron-bifurcating [FeFe]-hydrogenases from common bacterial groups being the dominant mechanism.
Summary
This study examined the genetic makeup of bacteria in the human colon to understand how they use molecular hydrogen (H2), a gas produced during digestion. Researchers found that 70% of colonic bacteria have the genetic ability to metabolize hydrogen, primarily through special proteins called [FeFe]-hydrogenases. The study suggests that hydrogen cycling in the gut works mainly through fermentation (a type of bacterial metabolism) and the transfer of hydrogen between different bacterial species, rather than through respiratory processes.
Practical Takeaway
This is a foundational genomic study that maps how gut bacteria naturally handle hydrogen, but it does not test hydrogen water or any health outcomes in humans. The findings may eventually help researchers understand gut health, but much more research is needed to determine whether consuming hydrogen water has any practical benefits for people.
Abstract
Microbial molecular hydrogen (H2) cycling is central to metabolic homeostasis and microbial composition in the human gastrointestinal tract. Molecular H2 is produced as an endproduct of carbohydrate fermentation and is reoxidised primarily by sulfate-reduction, acetogenesis, and methanogenesis. However, the enzymatic basis for these processes is incompletely understood and the hydrogenases responsible have not been investigated. In this work, we surveyed the genomic and metagenomics of hydrogenases in the human colon to infer dominant mechanisms of H2 cycling. The data demonstrate that 70% of gastrointestinal microbial species listed in the Human Microbiome Project encode the genetic capacity to metabolise H2. A wide variety of anaerobically-adapted hydrogenases were present, with [FeFe]-hydrogenases predominant. We subsequently analysed the hydrogenase gene content of stools from 20 healthy human subjects. The hydrogenase gene content of all samples was overwhelmingly dominated by fermentative and electron-bifurcating [FeFe]-hydrogenases emerging from the Bacteroidetes and Firmicutes. This study supports that H2 metabolism in the human gut is driven by fermentative H2 production and interspecies H2 transfer. However, it suggests that electron-bifurcation rather than respiration is the dominant mechanism of H2 reoxidation in the human colon, generating reduced ferredoxin to sustain carbon-fixation (e.g. acetogenesis) and respiration (via the Rnf complex). This work provides the first comprehensive bioinformatic insight into the mechanisms of H2 metabolism in the human colon.