Decoding E. coli's Gut Survival Strategies: A CRISPRi Approach Across Diets, Inflammatory Environment and Strains

Escherichia coli, a ubiquitous member of the mammalian gut microbiota, exhibits remarkable genetic diversity underpinning its commensal or pathogenic lifestyles. Deciphering the precise genetic determinants enabling E. colis adaptation within the complex and dynamic intestinal environment is critical for understanding host-microbe symbiosis and enteric disease pathogenesis. Here, we establish an in vivo CRISPR interference (CRISPRi) platform that leverages bacterial gene fitness profiles as a high-resolution functional reporter to define the molecular niche and selective forces encountered by E. coli within mice harboring a defined minimal microbial community (OligoMM12). Our investigation revealed that dietary regimens profoundly reshape E. colis metabolic landscape and that the profile of essential genes help identify cross-feeding interactions. Comparative screens across a laboratory strain (MG1655), a Uropathogenic, and Adherent-Invasive E. coli (AIEC), identify distinct genetic requirements for intestinal colonization, highlighting divergent motility, stress response, and respiration strategies. In a host inflammatory environment, we find that the AIEC strain LF82 alters its colonization pattern, shifting towards the small intestine, and adapts to the inflammatory environment by remodeling its metabolism and stress responses. Notably, we uncover a critical role for mobile genetic elements, with the observation that inflammation triggers the induction of the Gally prophage which is beneficial for fitness in the healthy gut but becomes detrimental during inflammation. These findings provide a high-resolution genetic atlas of E. colis functional adaptation and demonstrate the utility of functional genomics to probe the gut environment itself.