FIG. 1.

Northern blot analysis of rhlR, lecA, and lasB in the presence and absence of exogenous AHLs. P. aeruginosa cells were grown in LB broth in the absence or presence of 10 μM C4-HSL or 3O-C12-HSL. RNA was isolated from cells harvested throughout growth and separated by horizontal electrophoresis as detailed in Materials and Methods. The lecA and lasB structural genes were amplified with primers lecA1F and lecA1R and primers lasB1F and lasB1R, respectively. The rhlR gene was derived from pMW47.1 (23). The resulting products were labeled with [α-³³P]ATP and used as probes.