The Anaerobic Dissimilation of Citric Acid by Cell Suspensions of Streptococcus paracitrovorus

Abstract

Inasmuch as Str. paracitrovorus requires a complementary source of C for the utilization of citric acid for growth, previous studies on the dissimilation of this acid by growing cells have been confused by the presence of carbohydrate. It has been found that, cells grown in the presence of citrate plus lactose, when suspended in a N-free medium, can ferment citrate, oxaloacetate, and pyruvate. A scheme of dissimilation is presented. Evidence indicates that the dissimilation of citric acid proceeds through oxaloacetic and pyruvic acids as intermediates. The rate of fermentation of citrate, oxaloacetate, and pyruvate has been studied manometrically; the initial cleavage of citrate to oxaloacetic and acetic acids appears to be the limiting step in the dissimilation. Na azide, Na arsenite, and iodoacetate inhibit the fermentation of citric, oxaloacetic and pyruvic acids; NaF produces a slight inhibition; Na pyrophosphate has no effect.