H2 metabolism is diverse and widespread among human colonic microbes

Patricia G. Wolf, Ambarish Biswas, Sergio E. Morales, Christopher Andrew Greening, H. Rex Gaskins

Research output: Contribution to journalArticleResearchpeer-review

35 Citations (Scopus)

Abstract

Microbial molecular hydrogen (H2) cycling is central to metabolic homeostasis and microbial composition in the human gastrointestinal tract. 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 metagenomic distribution of hydrogenase-encoding genes 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 analyzed 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.
Original languageEnglish
Pages (from-to)235-245
Number of pages11
JournalGut Microbes
Volume7
Issue number3
DOIs
Publication statusPublished - 28 Apr 2016
Externally publishedYes

Keywords

  • electron-bifurcation
  • hydrogen
  • hydrogenase
  • hydrogenogen
  • hydrogenotroph
  • interspecies H2 transfer

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