Figure 1

Culturability and viability of L. pneumophila Philadelphia cells harvested at the beginning of stationary phase, before and after HOCl treatment. (A) Number of culturable cells as assessed on the standard medium (□), total number of cells detected using DAPI procedure (○), and viable cells detected using the CV6 procedure (◊) as a function of HOCl concentration (mM). The values reported are the means of three independent experiments (Errors bars = SD). Inset shows a close-up of the part of the plot corresponding to HOCl concentrations lower than 0.1 mM. Stars indicate that the number of culturable cells was significantly lower (p < 0.05) than the total number of cells. (B) Distribution of the normalized fluorescence intensity of the viable cells detected using the CV6 procedure as a function of HOCl concentration. Subpopulations were named according to their relative fluorescence intensity: L (Low), M (Medium) and H (High). (C) Distribution of the normalized fluorescence intensity of viable cells detected using the CV6 procedure in samples harvested from a culture in the exponential growth phase. For each condition, at least 3000 cells were analyzed. Similar results were obtained in two other independent experiments.