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Nat Commun. 2018 Jan 4;9(1):61. doi: 10.1038/s41467-017-02557-2.

Incomplete prophage tolerance by type III-A CRISPR-Cas systems reduces the fitness of lysogenic hosts.

Author information

1
Laboratory of Bacteriology, The Rockefeller University, New York, NY, 10065, USA.
2
Laboratory of Systems Cancer Biology, The Rockefeller University, New York, NY, 10065, USA.
3
Laboratory of Bacteriology, The Rockefeller University, New York, NY, 10065, USA. marraffini@rockefeller.edu.

Abstract

CRISPR-Cas systems offer an immune mechanism through which prokaryotic hosts can acquire heritable resistance to genetic parasites, including temperate phages. Co-transcriptional DNA and RNA targeting by type III-A CRISPR-Cas systems restricts temperate phage lytic infections while allowing lysogenic infections to be tolerated under conditions where the prophage targets are transcriptionally repressed. However, long-term consequences of this phenomenon have not been explored. Here we show that maintenance of conditionally tolerant type III-A systems can produce fitness costs within populations of Staphylococcus aureus lysogens. The fitness costs depend on the activity of prophage-internal promoters and type III-A Cas nucleases implicated in targeting, can be more severe in double lysogens, and are alleviated by spacer-target mismatches which do not abrogate immunity during the lytic cycle. These findings suggest that persistence of type III-A systems that target endogenous prophages could be enhanced by spacer-target mismatches, particularly among populations that are prone to polylysogenization.

PMID:
29302058
PMCID:
PMC5754349
DOI:
10.1038/s41467-017-02557-2
[Indexed for MEDLINE]
Free PMC Article

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