Control experiments required to validate each of the results in Table1. (a, b) Series of experiments corresponding to Figure 1, in absence of reverse transcriptase (RT) (no band expected). (c) Other RT-polymerase chain reaction (PCR) and PCR reaction controls. (M) Molecular Weight Marker VI (Boehringer Mannheim). Validation of RT reactions using kanamycin mRNA (kit control): water instead of matrix with kanamycin primers (lanes 1 and 5) (no band expected), with kanamycin mRNA (lanes 2 and 6) (band expected). Validation of PCR reaction using MG1655 E. coli genomic DNA: water instead of matrix with rpoD primers (lane3), or rpoS primers (lane 7) (no band expected), genomic DNA with rpoD primers (lane 4), or rpoS primers (lane 8) (band expected).