Reverse transcriptase-PCR analysis of the mcbABCI locus in pLQ510. (A) Schematic drawing showing the three sets of oligonucleotide primers that collectively spanned the three intergenic regions. (B) RT-PCR analysis of possible transcriptional linkage among the ORFs in the mcbABCI locus in pLQ510. RT-PCR was carried out as described in Materials and Methods. Lanes 1, 4, and 7 contain PCR products derived from pLQ510 DNA. Lanes 2, 5, and 8 are RT-PCR negative controls in which M. catarrhalis E22 RNA was incubated in the absence of reverse transcriptase. Lanes 3, 6, and 9 show the products obtained when these same primer pairs were used in RT-PCR with RNA from M. catarrhalis E22. Size markers (in bp) are present on the left side of panel B.