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

J Mol Biol. 2015 Nov 20;427(23):3754-65. doi: 10.1016/j.jmb.2015.09.010. Epub 2015 Sep 24.

Abstract

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.

Keywords: biofilms; self/non-self recognition; toxin/immunity proteins; type V secretion.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Review

MeSH terms

  • Amino Acid Sequence
  • Bacteria / growth & development*
  • Bacteria / immunology
  • Bacteria / metabolism
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / metabolism*
  • Bacterial Toxins / chemistry
  • Bacterial Toxins / metabolism
  • Biofilms
  • Escherichia coli Proteins / metabolism
  • Gene Expression Regulation, Bacterial
  • Genome, Bacterial
  • Gram-Positive Bacteria / growth & development
  • Gram-Positive Bacteria / metabolism
  • Membrane Proteins / metabolism
  • Microbial Consortia
  • Molecular Sequence Data
  • Protein Structure, Tertiary

Substances

  • Bacterial Proteins
  • Bacterial Toxins
  • CdiA protein, E coli
  • CdiB protein, E coli
  • Escherichia coli Proteins
  • Membrane Proteins