Ploidy is an important determinant of fluoroquinolone persister survival. Author Allison Murawski, Mark Brynildsen Publication Year 2021 Type Journal Article Abstract Genetic mutants have demonstrated the importance of homologous recombination (HR) to fluoroquinolone (FQ) persistence, which suggests that single-cell chromosome (Chr) abundance might be a phenotypic variable of importance to persisters. Here, we sorted stationary-phase E. coli based on ploidy and subjected the subpopulations to tolerance assays. Subpopulations sorted to contain diploid cells harbored up to ∼40-fold more FQ persisters than those sorted to contain monoploid cells. This association was observed with distinct FQs, in independent environmental conditions, and with more than one strain of E. coli (MG1655; uropathogenic CFT073) but was abolished in HR-deficient strains (ΔrecA and ΔrecB). It was observed that the persister level of monoploid subpopulations exceeded those of ΔrecA and ΔrecB by 10-fold or more, and subsequent high-purity sorting confirmed that observation. Those data suggested the existence of distinct FQ persister subtypes: those that are and are not proficient with HR. Time-lapse microscopy revealed significant differences in initial size and growth dynamics during the post-antibiotic recovery period for persisters from monoploid- and diploid-enriched subpopulations. In addition, non-persisters in monoploid-enriched subpopulations elongated minimally following FQ treatment, resembling previous observations of HR-deficient strains, whereas non-persisters in diploid-enriched subpopulations on average filamented extensively. Together, these results identify a phenotypic variable with a significant impact on FQ persistence, establish the existence of more than one type of persister to the same antibiotic in an isogenic culture, and reveal roles for RecA and RecB in FQ persistence, even in the absence of homologous chromosomes. Keywords Escherichia coli, Anti-Bacterial Agents, Escherichia coli Proteins, DNA-Binding Proteins, Fluoroquinolones, Rec A Recombinases, Exodeoxyribonuclease V, Ploidies Journal Curr Biol Volume 31 Issue 10 Pages 2039-2050.e7 Date Published 2021 May 24 ISSN Number 1879-0445 DOI 10.1016/j.cub.2021.02.040 Alternate Journal Curr Biol PMCID PMC8183807 PMID 33711253 PubMedPubMed CentralGoogle ScholarBibTeXEndNote X3 XML