Physiological Youth as an Important Factor in Adaptive Enzyme Formation

Abstract

Cells from a mature culture of Streptococcus lactis grown in glucose-tryptone broth can not attack galactose, lactose, sucrose or maltose at once, unless they have been allowed to multiply in the presence of that sugar. If cells are obtained from a glucose culture while still in the stage of physiological youth, they may attack these sugars either at once or with a short delay, even under conditions preventing proliferation. The most rapid adaptation to new sugars is always observed with cells from cultures just coming out of the lag phase, during the period of physiological youth. During the logarithmic phase, adaptability decreases rapidly and continuously. The ease of adaptation and the rate of loss of adaptability during the aging of a culture varies greatly with each sugar.