Fig. 7
From: Quorum sensing modulates the formation of virulent Legionella persisters within infected cells
The Lqs quorum-sensing system controls the formation of intracellular nongrowers. a–c lqsA promotes the formation of intracellular nongrowers. A. castellanii were infected (MOI 1, 24 h) with L. pneumophila WT, ΔlqsA or the complemented strain ΔlqsA(lqsA) expressing timer, and (a) fixed and analyzed by confocal microscopy or (b) lysed and analyzed by flow cytometry. Micrographs show the overlay of bright field and Timer fluorescence (500 and 600 nm). White arrows indicate intracellular nongrowers. Scale bar 10 μm. Histograms in black show the subpopulation fraction of intracellular nongrowers (black, left Y-axis) and absolute numbers of nongrowers (NG) in cell lysates are shown (yellow, right Y-axis). c A. castellanii were co-infected (MOI 1, 24 h) with L. pneumophila WT and ΔlqsA (ratio 10:1), expressing timer or not, lysed and the proportion of intracellular nongrowers in lysates was determined by flow cytometry. d Deletion of lqsA increases the antibiotic sensitivity of intracellular L. pneumophila. A. castellanii were infected (MOI 1, 24 h) with L. pneumophila WT or ΔlqsA expressing timer, lysed and released bacteria were treated (1 h) or not with of ofloxacin (3 μg mL−1). The percentage of surviving bacteria was determined by CFU. e Deletion of lqsA reduces the proportion in intracellular L. pneumophila expressing PflaA. A. castellanii were infected (MOI 1, 24 h) with L. pneumophila WT or ΔlqsA expressing PflaA-gfp, lysed and GFP producers were quantified by flow cytometry in lysates of infected amoebae. f The Lqs quorum-sensing system controls the formation of intracellular nongrowers. A. castellanii was infected (MOI 1, 24 h) with L. pneumophila WT, the isogenic ΔlqsS, ΔlqsT, ΔlqsS-ΔlqsT, or ΔlvbR mutant strains and the complemented strains ΔlqsS(lqsS), ΔlqsT(lqsT), or ΔlvbR(lvbR), ΔlqsS-ΔlqsT(lqsS), ΔlqsS-ΔlqsT(lqsT), expressing timer. After host cell lysis, the fraction of nongrowers was determined by flow cytometry. Data represent the mean ± SEM of at least three biological replicates (n ≥ 3; light gray filled circles). Student’s t test two-tailed. ***P < 0.001, **P < 0.01. Source data are provided as a Source Data file
