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. 2018 Jul 31;9:1699. doi: 10.3389/fmicb.2018.01699

FIGURE 6.

FIGURE 6

Effect of 10 cycles of sublethal aPDT exposure and regrowth, combined with 48 h growth under mild photodynamic stress, on development of resistance. After 10 cycles of photodynamic treatment and regrowth, cultures were diluted 100 fold in LB medium and allowed to grow for 48 h in the presence of ZnTnHex-2-PyP at final concentrations of 1.0 and 2.0 μM and light fluence of 0.5 mW/cm2. Stationary phase cultures obtained that way were diluted to OD600 = 0.5 in PBS, incubated for 30 min with 1.0 μM ZnTnHex-2-PyP and illuminated for 20 min at 37 mW/cm2. Cultures grown and illuminated in the absence of ZnTnHex-2-PyP were analyzed in parallel. Reduction of MTT to formazan is presented as a percentage of formazan formed by controls not exposed to any treatment. The “X” axis shows ZnTnHex-2-PyP concentrations during the 48 h growth under low light intensity (0.5 mW/cm2).