Detection of sRNAs in P. aeruginosa by Northern blots. Total RNA was purified from cultures of P. aeruginosa strain PAO1 grown in NYB until exponential phase (first lane in each blot) and stationary phase (second lane in each blot). Experimental conditions are described in Methods. The blots for the annotated sRNA genes encoding 4.5S RNA (in IgR 888), RNase P RNA (in IgR 2510) and PrrF1, 2 (in IgR 2667) are not shown. The approximate positions of RNA standards are shown on the left. The main transcripts are pointed out by arrows. A tRNACys gene is embedded in the IgR 1466; its transcript is indicated by an asterisk.