FIGURE 3.

Effect of repeated sublethal photodynamic treatment on Escherichia coli ability to replicate. All conditions were as in Figure 2. After the last illumination, cells were diluted and evenly spread on LB agar plates for enumeration of colonies (CFU assay). Cultures grown under the same conditions and subjected to the same treatment except exposure to PS, and original cultures not subjected to any treatment (controls), were tested in parallel. Results of two independent experiments, each sample in triplicate, are presented as medians and 25/75 percentiles [colony-forming unit (CFU)] surviving cells.