Stationary-phase Pseudomonas aeruginosa fluoroquinolone persisters mostly avoid DNA double-stranded breaks.

UNLABELLED: When susceptible bacterial cultures are treated with antibiotics, some cells can survive treatment without heritable resistance, giving rise to susceptible daughter cells in a phenomenon termed antibiotic persistence. Current models of fluoroquinolone (FQ) persistence in stationary-phase cultures posit that post-treatment resuscitation is dependent on double-stranded break (DSB) repair through RecA-mediated homology-directed repair. Previously, we reported that stationary-phase P. aeruginosa does not depend on RecA to persist. In this work, we ask whether P. aeruginosa FQ persisters from stationary-phase cultures suffer DSBs at all. We measured DSB formation in Levofloxacin (LVX)-treated cells recovering from treatment using strains expressing fluorescently labeled DSB-binding protein, Gam. We find that, surprisingly, the majority of P. aeruginosa LVX persisters survive treatment without apparent DSBs. Persisters that have evidence of DSBs take longer until their first division compared to persisters without DSBs. Additionally, the fates of their progenies suggest that persisters may cope with DSBs by repair or damage sequestration. These observations pave the way for mechanistic studies into P. aeruginosa FQ persistence and highlight the need for single-cell tools to track FQ-induced damage.

IMPORTANCE: Pseudomonas aeruginosa is an opportunistic pathogen of significant clinical interest. When susceptible cultures of P. aeruginosa are treated with fluoroquinolone (FQ) antibiotics, some cells survive treatment and regrow in a phenomenon termed antibiotic persistence. Studies in Escherichia coli and other bacterial species suggest that FQ persisters survive by repairing DNA double-stranded breaks (DSBs) after antibiotic removal. In this study, we show that most stationary-phase P. aeruginosa survive by avoiding DSBs rather than repairing them.