Understanding metabolic processes shaping adaptation of E. coli to the gut

Many microbes colonise the gut establishing interactions with their host and their nutritional environment. Studying genetics and metabolism brought about the drive and potential to engineer communities to promote health and improve industrial processes. However, structuring artificial communities in predictable ways is underdeveloped. We studied Escherichia coli’s genetic targets and physiological mechanisms during gut colonisation and adaptation and how metabolic environment/microbiota complexity shape these processes. We introduced a tractable E. coli K-12 in mice Germ-free or with polymicrobial communities. Whole Genome Sequencing identified potential adaptive targets. Here, we established phenotypic assays as well characterising effects of key mutations and metabolomics was performed with 1H-NMR of intestinal contents. Genes for sugar alcohol metabolism (gat) was the only target common to both mouse models, evidencing specificity. Facing complex microbiota E. coli targeted use of sugar alcohols (srlR, kdgR) and anaerobic respiration (dcuB, focA) [1] whereas alone, we observed instead mutations pointing to increased ability for amino acid use (lrp, dtpB, alaA). Mutations selected correlated dinamically with metabolomics: our results fit the model whereby other microbiota members scavenge oxygen and breakdown complex sugars, limiting E. coli to anaerobically respire simple by-product carbon sources. In the opposing scenario (functional absence) improved amino acid use are favoured colonisation factors. Through experimental evolution we gained insight on shaping E. coli’s metabolic traits through genetic engineering to colonise specific host environments. This work also highlights the versatility of E. coli as potential biotic sensor. [1] Barroso-Batista, J. et al. The first steps of adaptation of Escherichia coli to the gut are dominated by soft sweeps, 2014.