Composition of the human gut microbiota is a direct consequence of bacterial growth behavior and its strain to strain variation. Sure, faster growing bacterial species are more abundant than slower growing ones, but the exact growth rates depend in a complex way on the physiological conditions bacteria encounter locally throughout the intestine. Thus, to mechanistically understand the composition of our gut microbiota, we have to understand all the major factors influencing bacterial growth, how these factors are varying in space and time, and how their impact on growth behavior is varying from one bacterial species to the next.
These are very challenging tasks indeed. However we can already learn a lot about bacterial growth within the large intestine by quantitatively considering only a few major factors and their interactions. In our model we explicitly considered the interactions of nutrient inflow (the complex carbohydrates feeding the bacteria), local pH values, and intestinal flow (transit time).
So setup this model, we invested some time and effort to quantify different physiological processes and to find a reasonable level of mathematical description (realistic while simple enough). Full details are provided in the Supplementary Information of our paper.
Our findings suggest that pH and flow conditions are major factors affecting microbiota composition, capable of explaining the huge person to person variation in the microbiota composition observed on the phyla level.
We are currently extending these modeling considerations to better link bacterial growth dynamics to diet, eating manners, and host-physiological changes.
Interested in joining the lab?
We are looking for graduate students or postdocs to follow such a modeling approach (which can be combined with wet-lab approaches to characterize gut-bacteria or more epidemiological studies to study links of the gut-microbiota with diseases).