Sodium tolerance of L. pneumophila Lp ΔclpP mutant was enhanced. (A). Overnight bacterial cultures in mid-exponential phase were inoculated into fresh medium and grew to exponential phase (OD600 from 1.0 to 1.5) or stationary phase (OD600 from 3.5 to 4.5), then the CFU was determined by plating duplicate samples of JR32 (black bars), LpΔclpP mutant (white bars), and complemented strain (gray bars) on BCYE and BCYE containing 100 mM NaCl. The experiment was carried out in triplicate. * p < 0.01. (B). For direct visualization, different dilutions of stationary-phase JR32 and LpΔclpP cells were also spotted onto plates in triplicate.