Mechanisms of Resistance to the Contact-Dependent Bacteriocin CdzC/D inCaulobacter crescentus
Name
Cdz part II manuscript figures supplement.pdf
Description
Accepted version
Size
9.94 MB
Format
Adobe PDF
Checksum (MD5)
8b494f192ceed3f338e6da06c18d36c7
Author(s)
García-Bayona, Leonor
Gozzi, Kevin
Laub, Michael T
Date Issued
January 2019
Journal
Journal of Bacteriology
Publisher
American Society for Microbiology
Citation
García-Bayona, Leonor et al. "Mechanisms of Resistance to the Contact-Dependent Bacteriocin CdzC/D in Caulobacter crescentus." Journal of Bacteriology 201, 8 (January 2019): e00538-18 © 2019 American Society for Microbiology
Version
Author's final manuscript
Abstract
The Cdz bacteriocin system allows the aquatic oligotrophic bacterium Caulobacter crescentus to kill closely related species in a contact-dependent manner. The toxin, which aggregates on the surfaces of producer cells, is composed of two small hydrophobic proteins, CdzC and CdzD, each bearing an extended glycine-zipper motif, that together induce inner membrane depolarization and kill target cells. To further characterize the mechanism of Cdz delivery and toxicity, we screened for mutations that render a target strain resistant to Cdz-mediated killing. These mutations mapped to four loci, including a TonB-dependent receptor, a three-gene operon (named zerRAB for zipper envelope resistance), and perA (for pentapeptide envelope resistance). Mutations in the zerRAB locus led to its overproduction and to potential changes in cell envelope composition, which may diminish the susceptibility of cells to Cdz toxins. The perA gene is also required to maintain a normal cell envelope, but our screen identified mutations that confer resistance to Cdz toxins without substantially affecting the cell envelope functions of PerA. We demonstrate that PerA, which encodes a pentapeptide repeat protein predicted to form a quadrilateral β-helix, localizes primarily to the outer membrane of cells, where it may serve as a receptor for the Cdz toxins. Collectively, these results provide new insights into the function and mechanisms of an atypical, contact-dependent bacteriocin system. IMPORTANCE Bacteriocins are commonly used by bacteria to kill neighboring cells that compete for resources. Although most bacteriocins are secreted, the aquatic, oligotrophic bacterium Caulobacter crescentus produces a two-peptide bacteriocin, CdzC/D, that remains attached to the outer membranes of cells, enabling contact-dependent killing of cells lacking the immunity protein CdzI. The receptor for CdzC/D has not previously been reported. Here, we describe a genetic screen for mutations that confer resistance to CdzC/D. One locus identified, perA, encodes a pentapeptide repeat protein that resides in the outer membrane of target cells, where it may act as the direct receptor for CdzC/D. Collectively, our results provide new insight into bacteriocin function and diversity.
MIT Department
Massachusetts Institute of Technology. Department of Biology
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Creative Commons Attribution-Noncommercial-Share Alike
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DOI of Published Version
https://doi.org/10.1128/jb.00538-18
