The Effects of Oxygen and Carbon Dioxide on Proteinase Biosynthesis by Streptococcus Faecalis Var. Liquefaciens

The effect of O 2 and CO 2 on proteinase biosynthesis by nonproliferating cells of Streptococcus faecalis var. liquefaciens in chemically defined media were studied. In the absence of CO 2 , O 2 (1% in N 2 ) stimulated proteinase formation by promoting earlier synthesis and by increasing the rate of enzyme biosynthesis. Carbon dioxide under anaerobic conditions only enhanced the rate of proteinase synthesis. The stimulatory effect of the two gases was not additive. Glucose supported a greater yield of proteinase than galactose under all conditions of O 2 and CO 2 availability. Galactose was stimulatory in the presence of glucose only under aerobic conditions (1% O 2 in N 2 ) when atmospheric CO 2 was removed. Oxygen at the 20% level inhibited proteinase formation by increasing the rate of arginine disappearance from the medium.