Probiotic Escherichia coli Nissle 1917 Uses Zinc Transporters and the Siderophore Yersiniabactin to Acquire Zinc in the Inflamed Gut and Outcompete Salmonella Typhimurium

Objective Salmonella enterica serovar Typhimurium is a leading cause of foodborne illness worldwide. The pathogen elicits an inflammatory environment in the gut in which it can thrive. S . Typhimurium infection is ameliorated by the probiotic Escherichia coli Nissle 1917 ( E. coli Nissle), partly because E. coli Nissle expresses multiple iron transporters and siderophores, and outcompetes S . Typhimurium for iron. Here we sought to determine whether acquisition of the essential metal nutrient zinc also contributes to the probiotic activity of E. coli Nissle during S . Typhimurium infection and in a non‐infectious colitis model. Methods We generated S . Typhimurium and E. coli Nissle strains deficient in zinc uptake systems and compared their growth in zinc‐limited media. To test the importance of zinc transport systems in vivo , inflammation was elicited by dextran sodium sulfate and competitive infections with E. coli Nissle wild type and E. coli Nissle mutant strains were carried out. Furthermore, we infected streptomycin pre‐treated mice with S . Typhimurium and co‐administered wild type or mutant E. coli Nissle strains. To further investigate the mechanism by which E. coli Nissle reduces S . Typhimurium colonization, we used mice lacking the zinc‐sequestering protein calprotectin. Results We found that both S . Typhimurium and E. coli Nissle use the transporters ZnuABC and ZupT to acquire zinc in zinc‐limiting conditions. E. coli Nissle, but not S . Typhimurium, could additionally use the siderophore yersiniabactin for zinc acquisition. Yersiniabactin‐mediated zinc uptake rendered E. coli Nissle more resistant to zinc sequestration by the host protein calprotectin in vitro . Similarly, yersiniabactin was required for efficient colonization of E. coli Nissle in an inflamed environment in vivo . In competition with S . Typhimurium, E. coli Nissle required zinc transport systems and the presence of calprotectin to reduce S . Typhimurium colonization levels. In calprotectin‐deficient mice, yersiniabactin was dispensable for E. coli Nissle colonization, and E. coli Nissle was unable to reduce S . Typhimurium colonization. Conclusions Our findings demonstrate that zinc acquisition plays an important role in the competition between E. coli Nissle and S . Typhimurium. E. coli Nissle can use three mechanisms to acquire zinc: the zinc transporters ZnuABC and ZupT, as well as yersiniabactin, a siderophore that has been shown previously to bind other transition metals beside iron. Zinc acquisition systems and the host protein calprotectin contribute to E. coli Nissle's beneficial effects and the reduction of S . Typhimurium colonization of the inflamed gut.