FIG. 4.

Results of the RT-PCR experiments. Various stresses were applied to exponentially growing cells of S. aureus 8325 (A) and MA12 (B), as indicated at the bottom. Total RNA of the bacteria was isolated before and 5 and 20 min after exposure to the stress. Equal amounts of RNA (2 μg) were reverse transcribed to cDNA with random hexamer primers, and then the cDNA was subjected to PCR with gene-specific primers as described in Materials and Methods. For normalization of the samples 16S rRNA was used. The increase in expression of the nfrA mRNA at 5 and 20 min was calculated relative to the expression at zero time before stress was applied. Relative quantification of transcription was performed as described by Pfaffl (32). The data are the averages of two independent experiments.