FIG. 5.

RT-PCR to determine transcriptional status of ORFU, gtcA, and ORFD in L. monocytogenes serotype 4b. Primers P1 and P2 were used for cDNA synthesis. Subsequent PCR was done with primers P3 and P1 (lane 1), P4 and P1 (lane 2), P3 and P2 (lane 3), P2 and P4 (lane 4), and P2 and P5 (lane 5). No PCR product was observed in lanes 1 and 3. The leftmost lane contains molecular size markers. The location and orientation of the primers are shown at the bottom of the figure. Precise location and sequence of the primers as well as procedures for RT-PCR were as described in Materials and Methods. Templates for negative control were RNA with the same primer sets. None of the negative control reactions produced detectable PCR products (data not shown).