1. The hokW-sokW Locus Encodes a Type I Toxin–Antitoxin System That Facilitates the Release of Lysogenic Sp5 Phage in Enterohemorrhagic Escherichia coli O157
- Author
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Kosuke Takada, Kotone Hama, Takaomi Sasaki, and Yuichi Otsuka
- Subjects
bacteriophage ,Escherichia coli ,toxin–antitoxin system ,prophage induction ,Medicine - Abstract
The toxin-antitoxin (TA) genetic modules control various bacterial events, such as plasmid maintenance, persister cell formation, and phage defense. They also exist in mobile genetic elements, including prophages; however, their physiological roles remain poorly understood. Here, we demonstrate that hokW-sokW, a putative TA locus encoded in Sakai prophage 5 (Sp5) in enterohemorrhagic Escherichia coli O157: H7 Sakai strain, functions as a type I TA system. Bacterial growth assays showed that the antitoxic activity of sokW RNA against HokW toxin partially requires an endoribonuclease, RNase III, and an RNA chaperone, Hfq. We also demonstrated that hokW-sokW assists Sp5-mediated lysis of E. coli cells when prophage induction is promoted by the DNA-damaging agent mitomycin C (MMC). We found that MMC treatment diminished sokW RNA and increased both the expression level and inner membrane localization of HokW in a RecA-dependent manner. Remarkably, the number of released Sp5 phages decreased by half in the absence of hokW-sokW. These results suggest that hokW-sokW plays a novel role as a TA system that facilitates the release of Sp5 phage progeny through E. coli lysis.
- Published
- 2021
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