Strain competition restricts colonization of an enteric pathogen and prevents colitis

Aaron L. Hecht, Benjamin W. Casterline, Zachary M. Earley, Young Ah Goo, David R. Goodlett, Juliane Bubeck Wardenburg

Research output: Contribution to journalArticlepeer-review

100 Scopus citations


The microbiota is a major source of protection against intestinal pathogens; however, the specific bacteria and underlying mechanisms involved are not well understood. As a model of this interaction, we sought to determine whether colonization of the murine host with symbiotic non-toxigenic Bacteroides fragilis could limit acquisition of pathogenic enterotoxigenic B. fragilis. We observed strain-specific competition with toxigenic B. fragilis, dependent upon type VI secretion, identifying an effector–immunity pair that confers pathogen exclusion. Resistance against host acquisition of a second non-toxigenic strain was also uncovered, revealing a broader function of type VI secretion systems in determining microbiota composition. The competitive exclusion of enterotoxigenic B. fragilis by a non-toxigenic strain limited toxin exposure and protected the host against intestinal inflammatory disease. Our studies demonstrate a novel role of type VI secretion systems in colonization resistance against a pathogen. This understanding of bacterial competition may be utilized to define a molecularly targeted probiotic strategy.

Original languageEnglish
Pages (from-to)1281-1291
Number of pages11
JournalEMBO Reports
Issue number9
StatePublished - Sep 1 2016


  • colonization resistance
  • enterotoxigenic Bacteroides fragilis
  • in vivo strain competition
  • probiotics
  • type VI secretion


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