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Elife. 2017 Mar 21;6. pii: e24869. doi: 10.7554/eLife.24869.

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

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Department of Biology, Massachusetts Institute of Technology, Cambridge, United States.
Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, United States.
Graduate Program in Microbiology, Massachusetts Institute of Technology, Cambridge, United States.


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.


Caulobacter crescentus; bacteriocins; contact-dependent inhibition; infectious disease; microbiology; type I secretion system

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