EFFECT OF ACETATE, CITRATE, AND DIVALENT METAL IONS ON UTILIZATION OF SODIUM CASEINATE BY LACTIC STREPTOCOCCI

Abstract

Growth of caseinate utilizing lactic streptococci in media with sodium caseinate as the nitrogen source was retarded by sodium acetate (40 mg./ml.) and by sodium citrate (10 mg./ml.). The inhibition caused by citrate was relieved by calcium or magnesium while that caused by acetate was relieved by calcium. In media with acid hydrolyzed casein as the nitrogen source, growth was inhibited in the presence of sodium citrate (10 mg./ml.) or disodium ethylene diamine tetraacetate (0.004 mg./ml.) but this inhibition was overcome by the addition of either calcium or magnesium. It appears, therefore, that these divalent ions were not required merely for activation of proteases produced by the organisms.