Figure 1. CLS extension is dependent upon the timing of NaHS treatment. Viabilities of cells treated without (black plots) or with 100 μM NaHS at the earlier (blue plots) or the later (red plots) phases of growth were plotted. Specifically, NaHS was added once or twice into cell cultures at the 12 hours (A), 24 and 48 hours (B), 84 hours (C), 96 hours (D), or 72 and 96 hours (E) after inoculation. (F) NaHS was added into cell cultures every 24 hours after 72 hours of inoculation. Arrows indicate the time of NaHS treatment. Triplicate cultures were used to achieve mean ± SD of viabilities. *p < 0.05, **p < 0.01, ***p < 0.001.