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

In Pseudomonas aeruginosa ATCC 10145 a negative correlation was observed between the protonmotive force (delta P) and the amount of exoprotease produced, with a decrease in delta P resulting in an increase in exoprotease. The two components of delta P, the transmembrane pH gradient (delta pH) and the membrane potential (delta psi) were examined independently and it was observed that delta psi 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, delta pH became more alkaline and increased exoprotease activities were recorded. Furthermore, an increase in extracellular pH to give an artificial alteration in delta pH, and, consequently, a decrease in delta P, increased exoprotease production, thus confirming the importance of delta pH in exoprotease production.