RegIIIβ promotes Salmonella Typhimurium colonization of the gut in the early-stage gastrointestinal infection by enhancing flagella-driven locomotion

The bactericidal lectin RegIIIβ secreted by intestinal epithelial cells, kills the microbiota and enteropathogens but also been suggested to modulate bacterial physiology and host interactions. However, it remains to be determined whether RegIIIβ plays roles beyond its bactericidal effects. The present study revealed that RegIIIβ binds to the enteropathogen Salmonella enterica serovar Typhimurium in the gut, thereby increasing the locomotion speed of this bacterium through maintenance of the membrane potential. This led to enhanced invasion by S. Typhimurium into epithelial cells. Finally, RegIIIβ facilitated the gut colonization levels of S. Typhimurium and enteropathy in the early stages of gastrointestinal infection. In conclusion, S. Typhimurium has become tolerant to RegIIIβ in the evolutionary process, during which the pathogen has simultaneously acquired the ability to exploit this antimicrobial to enhance flagellar-based locomotion for successful gastrointestinal infection. Our findings provide novel insight into the roles of RegIIIβ in gastrointestinal infection caused by S. Typhimurium.