A cartoon of a woman eating broccoli, with the digestive tract shown on her shirt, and smiling microbes in the background.

Human microbiome

Human health is a complicated thing to define, and can be even trickier to understand when factoring in whether our microbes are helping or harming. We carry trillions of microbial cells in our mouth and digestive tract, and to a lesser extent on our skin, in our lungs, or in our vaginas. Which and how many bacteria, archaea, fungi, viruses, or protozoa (collectively, the microbiome) might inhabit our bodies is impacted by myriad factors, including our lifestyle, ecology, age, health status, and diet.

In particular, the digestive tract is a universe for microorganisms: some pass through but once, some are frequent tourists, and some spend their entire existence in the confines of the gut.  Each microorganism brings with it an array of capabilities for digesting or producing different chemical compounds. In many cases, the human host is reliant on these microbial functions to digest its diet and maintain a hesitant truce with the more exuberant members of the gut community. Each organ in the digestive tract creates a unique environment, with variations in temperature, oxygen content, pH, salinity, muscle contractions, human cells, and human enzymes.  These conditions, and their effect on the diet as it moves through the gut, combine as selective factors for which and how many microorganisms thrive in any location.  This effect on the microbial communities requires us to use spatial resolution in our studies – or sampling multiple locations along the gut.  Yet, this is invasive and logistically difficult to do in humans if we need to research anything beyond the mouth but before the distal colon. Much of my lab focuses on understanding the players and the dynamics in the microbial universe that is the digestive tract, and combines research on microbes, animals, and humans to collectively understand how microbes and humans interact.

Relevant Reviews

  1. Holman, J., Hurd, M., Moses, P.,  Mawe, G.,  Zhang, T., Ishaq, S.L., Li, Y. 2022. Interplay of Broccoli/Broccoli Sprout Bioactives with Gut Microbiota in Reducing Inflammation in Inflammatory Bowel DiseasesJournal of Nutritional Biochemistry 113:109238
  2. Ishaq, S.L., Rapp, M., Byerly, R., McClellan, L.S., O’Boyle, M.R., Nykanen, A., Fuller, P.J., Aas, C., Stone, J.M., Killpatrick, S., Uptegrove, M.M., Vischer, A., Wolf, H., Smallman, F., Eymann, H., Narode, S., Stapleton, E., Cioffi, C.C., Tavalire, H.. 2019. Framing the discussion of microorganisms as a facet of social equity in human health. PLoS Biology 17(11): e3000536. Microbiomes Across Systems special issue. Essay. Impact 8.386. 
  3. Ishaq S.L., Wright A-D.G., Moses, P.L. 2016. Ch 2: The pathology of methanogenic archaea in human gastrointestinal disease. In: The Gut Microbiome – Implications for Human Disease. Mozsik, G. (ed.). InTech. Pp. 19-37.

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