Ecology of the intestinal microbe, Faecalibacterium prausnitzii

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Microbial communities (microbiota) in the gut digest our food and protect us against infectious organisms. How the microbiota contribute to these processes is known in only a few specific cases, partly due to the enormous diversity of microbes (more than 1000 species in our gut) and the complexity of their interactions with each other and with us. In this proposed research, I will explore some of these interactions in the context of a simplified microbiota (12 species), with a focus on a key microbe, Faecalibacterium prausnitzii. Experiments will be conducted in mice and in community culture systems. The bacterial species, F. prausnitzii, is a dominant member of the microbiota in the colon of healthy adults. This is the part of the gut where complex foods are digested and absorbed, and F. prausnitzii is thought to be a key contributor to these processes. F. prausnitzii digests dietary fiber as a source of energy and produces an important metabolite, butyrate, which has beneficial effects on colon health. In addition, F. prausnitzii has been shown to secrete a variety of molecules that reduce gut inflammation through mechanisms of communication with the intestinal immune system that are only partially known. The conditions necessary for promoting these functions are not known. Intestinal inflammation, which is a normal response to infection, is a significant stress on the microbiota and can lead to transient or sometimes long-term changes in community composition (i.e. some species die while others flourish) and behavior (i.e. switch to survival mode). F. prausnitzii levels are dramatically reduced in the inflamed gut, suggesting that this organism is sensitive to changes in the gut ecosystem. There is currently great interest in developing therapies based on restoring the healthful qualities of this species for patients with chronic inflammatory diseases such as Crohn's disease. To do so will require a better understanding of how F. prausnitzii, as well as other members of the microbiota, regulate their interactions with the intestinal environment, other members of the microbiota and the intestinal immune system to restore gut processes. This understanding will contribute to our overall understanding of a healthy gut.