Figure 1.
Viability and intracellular ATP levels of M. bovis BCG during the hypoxic shift down assay. (a) Upper row: A hypoxic M. bovis culture was inoculated at an OD600 of 0.2 in a 24-well plate and shifted into a hypoxic atmosphere. The presence of oxygen left in the culture was monitored by decolorization of methylene blue. Methylene blue decolorized after 2 days. Lower row: Control wells with methylene blue, but without bacilli, in a hypoxic atmosphere. (b) ATP levels (RLU, relative luminescence units) were monitored daily for a period of 7 days. (c) Survival of M. bovis BCG and M. bovis BCG:ΔdosR in the hypoxic shift down model. Viability (CFU/mL) of M. bovis BCG parental (black bar), M. bovis BCG:ΔdosR (white bar), and complemented mutant (gray bar) was determined at each time point in the hypoxic shift down model. The experiment was carried out three times in triplicate, and results are given as means ± SD.