Periodic Reporting for period 1 - H2Gut (Interspecies hydrogen transfer in the mammalian gut: how interactions between fermenters and hydrogenotrophs influence colonic homeostasis)
Reporting period: 2018-09-01 to 2020-08-31
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.
To identify which microorganisms in the human gut actively metabolize hydrogen, we incubated fresh human fecal samples from 7 donors in the presence of hydrogen gas and sorted out individual cells that were active in the incubations. This single-cell approach enabled us to quickly and efficiently sort and identify which microorganisms were the most active hydrogen utilizers in human fecal samples. We compared the active hydrogen utilizers that we recovered in the incubations with the microorganisms that were expressing hydrogenases and used this data to construct transcript maps (maps of gene expression) for the organisms that were active and contributed to hydrogenase expression. We analyzed the transcript maps of these keystone hydrogen metabolizing organisms to characterize the metabolic pathways they use for fermentation and/or hydrogen utilization.