Critical cross feeding mechanisms of microbial communities in the gut: menaquinone production and bacterial bioenergetics

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Microbes interdepend on community members that are close in proximity for nutrients and other molecules. Highlighting the importance of certain metabolic by-products from bacterial community associates, a recent discovery from our group showed that acetate delivered to the colon could heavily promote keystone bacterial symbionts. Acetate is a short chain fatty acid which is usually rapidly taken in by the host and is not present in the colon in significant amounts. Its presence in the colon is typically only as a by-product of bacterial fermentation in small amounts. Akkermansia muciniphila is particularly stimulated by acetate which concurrently increased the microbial biosynthesis of menaquinone (MK; vitamin K2) with other bacterial members. MK is an important vitamin for both mammals and also bacteria in the process of energy generation. There is a paucity of information on the unique components that commensal bacteria for energy generation. Our new data suggests that bacteria in a broader community context may not be as selfish as they are traditionally perceived. We hypothesise that community sharing of molecules involved in energy generation, such as MK is a critical factor regulating the dynamic evolution of gut microbial communities. Here, we aim to better understand the major mechanistic interplay within the gut microbiota by this respiratory molecule. Our first objective encompasses using a gut model where we will screen for different acetate types which promote A. muciniphila and then monitor how altered MK biosynthesis impacts the system. We will collect a bacterial library for further analysis and examine the type of MK variant produced. The second objective will decipher the impact and transference of different bacterial MK types in pure and mixed bacterial cultures. These studies will help to bridge the knowledge gap to improve our understanding of human gut-associated microbial communities by characterizing the underlying energy-generating networks which support the co-existing of host-adapted species. Moreover, the findings will be applicable to broad aspects of microbial ecology, health and the food industry.