Contact-dependent growth inhibition requires the essential outer membrane protein BamA (YaeT) as the receptor and the inner membrane transport protein AcrB

Stephanie K. Aoki, Juliana C. Malinverni, Kyle Jacoby, Benjamin Thomas, Rupinderjit Pamma, Brooke N. Trinh, Susan Remers, Julia Webb, Bruce A. Braaten, Thomas J. Silhavy, David A. Low

Research output: Contribution to journalArticlepeer-review

117 Scopus citations

Abstract

Contact-dependent growth inhibition (CDI) is a phenomenon by which bacterial cell growth is regulated by direct cell-to-cell contact via the CdiA/CdiB two-partner secretion system. Characterization of mutants resistant to CDI allowed us to identify BamA (YaeT) as the outer membrane receptor for CDI and AcrB as a potential downstream target. Notably, both BamA and AcrB are part of distinct multi-component machines. The Bam machine assembles outer membrane β-barrel proteins into the outer membrane and the Acr machine exports small molecules into the extracellular milieu. We discovered that a mutation that reduces expression of BamA decreased binding of CDI+ inhibitor cells, measured by flow cytometry with fluorescently labelled bacteria. In addition, α-BamA antibodies, which recognized extracellular epitopes of BamA based on immunofluorescence, specifically blocked inhibitor-target cells binding and CDI. A second class of CDI-resistant mutants identified carried null mutations in the acrB gene. AcrB is an inner membrane component of a multidrug efflux pump that normally forms a cell envelope-spanning complex with the membrane fusion protein AcrA and the outer membrane protein TolC. Strikingly, the requirement for the BamA and AcrB proteins in CDI is independent of their multi-component machines, and thus their role in the CDI pathway may reflect novel, import-related functions.

Original languageEnglish (US)
Pages (from-to)323-340
Number of pages18
JournalMolecular Microbiology
Volume70
Issue number2
DOIs
StatePublished - Oct 2008

All Science Journal Classification (ASJC) codes

  • Microbiology
  • Molecular Biology

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