Metabolism of exogenous arginine and glucose by starved Streptococcus lactis in relation to survival.

Abstract

SUMMARY: Arginine or glucose accelerated death of Streptococcus lactis starved in phosphate buffer. Both substrates were metabolized at linear but different rates and the rate of ATP production from glucose metabolism was about 7.5 times that for arginine metabolism. Mg2+ reduced glucose-accelerated death and abolished arginine-accelerated death to prolong survival. When glucose was fed continuously to organisms starved in phosphate buffer containing Mg2+, survival was related to the rate of glucose addition and hence to the rate of metabolism. By feeding low concentrations of glucose, the viability of most of the population was extended from about I to 4 days. The maintenance energy requirement appeared to be in the region of 0.045 to 0.09 mg. glucose/mg. dry wt bacteria/hr. The glycolytic activity of starved organisms declined at varying rates depending on the starvation environment but could not be correlated directly with loss of viability. Exogenous arginine substantially reduced the lethal effect of adverse pH values.