FIG. 5.

Release of PA into the extracellular medium. (A) E. coli K5 cells transformed with pPAEC (control) and pPAK2 were grown at 28°C in LB medium supplemented with 25 μg of chloramphenicol/ml. Plasmid-carried pac and kil genes were induced with 0.5 mM IPTG; thereafter, at the times indicated, 1-ml samples were withdrawn. The PA activity in kil-expressing cells was measured in homogenized cells (periplasm) and in the culture supernatant (extracellular). (B) E. coli K5(pPAK2) cells were cultivated in different media as described for the cultivation in panel A. At 6 h after IPTG induction, PA activity was measured in the supernatant (extracellular) and in homogenized cells (periplasm). LB, LB medium; M9, M9 minimal medium.