The Protonmotive Force in Pseudomonas aeruginosa and its Relationship to Exoprotease Production

SUMMARY: In Pseudomonas aeruginosa ATCC 10145 a negative correlation was observed between the protonmotive force (δP) and the amount of exoprotease produced, with a decrease in δP resulting in an increase in exoprotease. The two components of δP, the transmembrane pH gradient (δpH) and the membrane potential (δ) were examined independently and it was observed that δ varied very little under the conditions which influenced the activities of exoprotease. However, a positive correlation existed between pH and exoprotease production although the intracellular pH varied very little with either changes in growth rate or changes in extracellular pH. It was observed that with a decrease in growth rate, δpH became more alkaline and increased exoprotease activities were recorded. Furthermore, an increase in extracellular pH to give an artificial alteration in δpH, and, consequently, a decrease in δP, increased exoprotease production, thus confirming the importance of δpH in exoprotease production.