Contact-Dependent Growth Inhibition (CDI) and CdiB/CdiA Two-Partner Secretion Proteins

Julia L.E. Willett, Zachary C. Ruhe, Celia W. Goulding, David A. Low, Christopher S. Hayes

Research output: Contribution to journalReview article

43 Scopus citations


Bacteria have developed several strategies to communicate and compete with one another in complex environments. One important mechanism of inter-bacterial competition is contact-dependent growth inhibition (CDI), in which Gram-negative bacteria use CdiB/CdiA two-partner secretion proteins to suppress the growth of neighboring target cells. CdiB is an Omp85 outer-membrane protein that exports and assembles CdiA exoproteins onto the inhibitor cell surface. CdiA binds to receptors on susceptible bacteria and subsequently delivers its C-terminal toxin domain (CdiA-CT) into the target cell. CDI systems also encode CdiI immunity proteins, which specifically bind to the CdiA-CT and neutralize its toxin activity, thereby protecting CDI+ cells from auto-inhibition. Remarkably, CdiA-CT sequences are highly variable between bacteria, as are the corresponding CdiI immunity proteins. Variations in CDI toxin/immunity proteins suggest that these systems function in bacterial self/non-self recognition and thereby play an important role in microbial communities. In this review, we discuss recent advances in the biochemistry, structural biology and physiology of CDI.

Original languageEnglish (US)
Pages (from-to)3754-3765
Number of pages12
JournalJournal of Molecular Biology
Issue number23
StatePublished - Nov 20 2015


  • Abbreviations CDI contact-dependent growth inhibition
  • ORF open reading frame
  • TPS two-partner secretion
  • pmf proton motive force

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