Shigella sonnei Encodes a Functional T6SS Used for Interbacterial Competition and Niche Occupancy

Cell Host Microbe. 2017 Jun 14;21(6):769-776.e3. doi: 10.1016/j.chom.2017.05.004.


Shigella is a leading cause of dysentery worldwide, with the majority of infections caused by two subgroups, S. flexneri and S. sonnei. Although S. flexneri has been highly prevalent in low-income countries, global development has brought an increase in S. sonnei at the expense of S. flexneri. However, the mechanisms behind this shift are not understood. Here we report that S. sonnei, but not S. flexneri, encodes a type VI secretion system (T6SS) that provides a competitive advantage in the gut. S. sonnei competes against E. coli and S. flexneri in mixed cultures, but this advantage is reduced in T6SS mutant strains. In addition, S. sonnei can persist as well as outcompete E. coli and S. flexneri in mice in a T6SS-dependent manner. These findings suggest that S. sonnei has a competitive advantage over S. flexneri and potentially explain the increasing global prevalence of S. sonnei.

Keywords: S. sonnei; Type VI Secretion; bacterial competition; virulence and colonization.

MeSH terms

  • Animals
  • Antibiosis / physiology
  • Coculture Techniques
  • Colon / microbiology
  • Colon / pathology
  • Colony Count, Microbial
  • Disease Models, Animal
  • Dysentery, Bacillary / microbiology*
  • Escherichia coli / drug effects
  • Escherichia coli / growth & development
  • Female
  • Guinea Pigs
  • Lactobacillus / growth & development
  • Mice
  • Mice, Inbred BALB C
  • Microbial Interactions
  • Mutation
  • Shigella flexneri / drug effects
  • Shigella flexneri / genetics
  • Shigella flexneri / growth & development
  • Shigella sonnei / genetics
  • Shigella sonnei / growth & development
  • Shigella sonnei / metabolism*
  • Type VI Secretion Systems / genetics*
  • Type VI Secretion Systems / pharmacology
  • Type VI Secretion Systems / physiology*


  • Type VI Secretion Systems