The effect of ionophores on the production of extracellular dextransucrase by Leuconostoc mesenteroides

The effects of several ionophores on the production of extracellular dextransucrase by Leuconostoc mesenteroides were examined at different pH values. Valinomycin severely inhibited extracellular dextransucrase production at culture pH values greater than 6.3 in complex medium containing 250 mM K+. The inhibitory action of valinomycin was a function of the culture pH as no effect on dextransucrase production could be demonstrated at pH 5.5. The ΔpH dissipating agent nigericin did not inhibit dextransucrase production at a culture pH of 6.4 but affected it severely as the pH decreased. Extracellular dextransucrase was not detected in cultures treated with a combination of valinomycin and nigericin. The results suggest a role for the total protonmotive force in the production of extracellular dextransucrase by L. mesenteroides.