Analysis of stationary-phase Mga-regulated gene expression in serotype M6 KSM148 sptR mutants. (A) Northern analysis of wild-type KSM148 (148), mga-inactivated KSM148.586 (586), and the 12 sptR mutants (1R, 2R, and 4R to 13R). Total RNA (1 μg of total RNA for exponential-phase KSM148; 5 μg of total RNA for all stationary-phase samples) was probed for emm6 transcript levels. Northern blots were stripped and reprobed for 23S RNA as a control for loading. (B) Mga protein levels in each stationary-phase lysate were determined by Western blotting (7 μg of total protein), with an antibody to a peptide of Mga used as a probe.