FIG 2.
σB-mediated resistance to RIF is independent of ADP-ribosyltransferase (Arr) and putative effector genes. (a) Wild-type M. smegmatis (MsWT) and the MsΔsigB strain were grown to an A600 of 0.7 and exposed to 4 μg/ml RIF for either 20 min or 2 h, and the amount of M. smegmatis arr transcripts was determined by qPCR and plotted as the fold induction over the level of expression for an unexposed control. Data represent the mean ± SD (n = 3). sigA was used as an endogenous control. (b) Tenfold serial dilutions of WT strain M. smegmatis mc2155 and the MsΔarr and MsΔsigB MsΔarr strains were grown to an A600 of 0.7 and spotted on Middlebrook 7H10 ADC containing the indicated concentration of RIF.