FIG. 3.
Development of stress resistance to heat (A; 62°C for 30 min), acid (B; pH 3.3 for 30 min), NaOCl (C; 10−2% [vol/vol] for 8 min), and UV254 nm irradiation (D; 180 J/m2) in E. faecalis during incubation in tap water. Before transfer into the aquatic system, the cultures were harvested from the exponential-growth phase (○) or at the onset (•) or after 24 h (□) of glucose starvation. Values shown on the ordinate represent the sensitivities of the control cultures prior to transfer into the microcosm. For all stresses, the resistance of preadapted glucose-starved control cultures was initially significantly higher than that of exponentially growing cells. The data are means and standard deviations (bars) for at least three independent experiments.