Growth in acidic medium. BCG (pMV261) and BCG (pAS-MDP1) were grown in Mb/OADC medium adjusted to pH 7 (A, B) or pH 5.3 (C, D), respectively, and the growth of the mycobacteria was monitored by measurement of the OD [600 nm] (A, C) and the amount of ATP in the cultures (B, D). The ATP amount was measured using a luminescence assay and is reported as relative light units (RLU). Each value represents the mean of three cultures with the standard deviation. The results of a paired student’s t test are shown by asterisks (*: P < 0.05, **: P < 0.01).