Expression of perA in MMH594 and E99 by RT-PCR. Primers perA-FF and perA-RR (Table 2), specific to perA, were used in all reactions. RT(−) controls indicate samples are free of contaminating genomic DNA. Lanes: 1, E99 DNA; 2, E99 RT(+); 3, MMH594 RT(+); 4, E99 RT(−); 5, MMH594 RT(−); 6, MMH594 DNA. Lane M is a 1-kb size marker from New England Biolabs.