Dynamics of glucose consumption in yeast

When a continuously grown yeast culture was allowed to rest at the low dilution rate for an extended time period and was then challenged by increasing the dilution rate, applied as a step function, an overshoot of the concentration of residual glucose occurred reproducibly. A structural extension of the bottleneck model describing another intracellular bottleneck in glucose consumption allowed to predict such overshoots quantitatively. The model assumes that an intracellular enzymatic pool increases in response to a challenge by excess substrate supply, and experimentally, the relaxation time was determined to be on the order of 1 h. When the culture is reset to more limiting conditions, the enzymatic pool shrinks with a relaxation time determined by the reciprocal of the current specific growth rate. Generalized, microbial populations do memorize their (recent) history by adapting their metabolic outfit.