Contact-dependent killing by Caulobacter crescentus via cell surface-associated, glycine zipper proteins

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Abstract

Most bacteria are in fierce competition with other species for limited nutrients. Some bacteria can kill nearby cells by secreting bacteriocins, a diverse group of proteinaceous antimicrobials. However, bacteriocins are typically freely diffusible, and so of little value to planktonic cells in aqueous environments. Here, we identify an atypical two-protein bacteriocin in the α-proteobacterium Caulobacter crescentus that is retained on the surface of producer cells where it mediates cell contact-dependent killing. The bacteriocin-like proteins CdzC and CdzD harbor glycine-zipper motifs, often found in amyloids, and CdzC forms large, insoluble aggregates on the surface of producer cells. These aggregates can drive contact-dependent killing of other organisms, or Caulobacter cells not producing the CdzI immunity protein. The Cdz system uses a type I secretion system and is unrelated to previously described contact-dependent inhibition systems. However, Cdz-like systems are found in many bacteria, suggesting that this form of contact-dependent inhibition is common.

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Leonor Garcia-Bayona

Department of Biology, Massachusetts Institute of Technology, Cambridge, United States

Competing interests
No competing interests declared.
Monica S Guo

Department of Biology, Massachusetts Institute of Technology, Cambridge, United States

Competing interests
No competing interests declared.
Michael T Laub

Department of Biology, Massachusetts Institute of Technology, Cambridge, United States

For correspondence
laub@mit.edu

Competing interests
Michael T Laub, Reviewing editor, eLife.

"This ORCID iD identifies the author of this article:" 0000-0002-8288-7607

Funding

National Institutes of Health (R01GM082899)

Michael T Laub

Howard Hughes Medical Institute

Leonor Garcia-Bayona
Michael T Laub

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

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This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.