FIG. 7.

An increase in transcript levels of yfiA (A) and fis (B) in the Δpnp cells is due to stabilization of the respective mRNAs. Total RNAs were isolated from wild-type and Δpnp cells by the hot phenol method. The exponentially growing cells were cold shocked at 15°C for 1 h (for the yfiA gene) or 72 h (for the fis gene), the transcription was stopped by adding rifampin, and samples were collected for RNA isolation at the times indicated in the figure. Equal amounts of RNA samples were used for primer extension with deoxyoligonucleotides corresponding to the yfiA or fis gene. The products were analyzed by 6% polyacrylamide gel electrophoresis under denaturing conditions.