Monosaccharides Drive Salmonella Gut Colonization in a Context-Dependent Manner

The carbohydrates that fuel gut colonization by S. Typhimurium are not fully known. To investigate this, we designed a quality-controlled mutant pool to probe the metabolic capabilities of this enteric pathogen. Using WISH-barcoding, we tested 35 metabolic mutants across five different mouse models, allowing us to differentiate between context-dependent and context-independent nutrient sources. Results showed that S. Typhimurium uses D-glucose, D-mannose, D-fructose, and D-galactose as context-independent carbohydrates across all models. The utilization of N-acetylglucosamine and hexuronates, on the other hand, was context-dependent. Furthermore, we showed that D-fructose is important in strain-to-strain competition between Salmonella serovars. Complementary experiments confirmed that D-glucose, D-fructose, and D-galactose are excellent niches for S. Typhimurium to exploit during colonization. Quantitative measurements revealed sufficient amounts of D-glucose and D-galactose in the murine cecum to drive S. Typhimurium colonization. Understanding these key substrates and their context-dependent use by enteric pathogens will inform the future design of probiotics and therapeutics to prevent diarrheal infections such as non-typhoidal salmonellosis.