Variations in dehydrogenase and deaminase activity during bacterial growth

Abstract

Apart from a gradual decay in the stationary phase, the glucose and succinic dehydrogenase per unit mass are roughly constant (at high and low values, respectively) during the growth cycle of Bact. lactis aerogenes in a glucose-ammonium sulphate medium. Asparagine deaminase per unit mass rises steeply towards the end of the growth cycle as the medium grows acid, an increased amount tending to compensate the lower specific activity at the adverse pH. During the early stages of a growth cycle started with an inoculum of this high deaminase content the enzyme activity per unit mass rapidly falls by dilution with new material of lower content. During the long lag shown by the cells on an initial transfer to a medium containing succinate in place of glucose the asparagine deaminase content rises and, after growth begins, falls again. The glucose dehydrogenase remains unchanged, while the succinic dehydrogenase, once growth begins, rapidly rises to a value very much higher than the original[long dash]requiring, however, several subcultures in succinate to reach its optimum. Succinate-adapted cells do not again show the abnormal initial increase in deaminase. On retransfer to a glucose medium succinate-adapted cells rapidly lose their high succinic dehydrogenase activity, but only very slowly develop a lag in succinate. Adaptation to succinate appears to involve more than one enzyme system.