Hydrogen gas is an important metabolite formed in our gut solely by microorganisms when indigestible components of our diet such as fibre (polysaccharides) are broken down and fermented. Hydrogen that is produced in the human gut builds up to relatively high levels after a meal (0.5-3% by volume) and must be disposed of very efficiently because the buildup of this gas strongly inhibits fermentation and overall function of the gut. Four different groups of anaerobic organisms exist in the gut that can consume this hydrogen and prevent its harmful accumulation: bacteria that produce sulfide (sulfidogens), archaea that produce methane (methanogens), bacteria that produce acetate when they breathe carbon dioxide (acetogens), and bacteria that breathe fumarate. Although we know that microbial hydrogen gas metabolism in the gut has a strong influence on our gut health, we do not know which organisms produce or consume this gas in our gut. We have only limited knowledge of which organisms have the potential to metabolize this important gas in the human gut and only rudimentary knowledge of which organisms actively metabolize hydrogen in the human gut.
Understanding hydrogen gas formation and consumption in the human gut by our microflora is important because it allows us to understand how the presence of various microbes and how different diets may influence our health. For example, eating a high fibre diet may result in high hydrogen production in the human gut which could stimulate hydrogen-consuming bacteria to produce more acetate – a metabolite that plays an important role in prevention/treatment of metabolic syndromes, bowel cancer, and bowel disorders. On the other hand, some pathogens like Salmonella take advantage of hydrogen produced during fibre breakdown to infect and grow in the gut. Characterizing which microbes actively produce and consume hydrogen in the human gut will allow us to better understand how our microbiome, our diet, and incoming pathogens influence our health.
The overall objectives of this project are to: 1) identify which microbes and pathways might contribute to hydrogen production and consumption in the gut, 2) assess which pathways and which microbes express their hydrogenases, 3) to determine which microbes are active hydrogen utilizers, and 4) to integrate the new results into a hypothesis about which organisms are the most important hydrogen metabolizers in the human gut.
