Autonomous oscillations in Saccharomyces cerevisiae during batch cultures on trehalose

Abstract

We report that autonomous oscillations, which usually happen in aerobic glucose-limited continuous cultures of yeast at low dilution rate, were also observed in trehalose discontinuous cultures of Saccharomyces cerevisiae. This unexpected oscillatory behaviour was therefore examined using fast Fourier transformation of online gas measurements. This robust mathematical analysis underlined the existence of two types of oscillation. The first was found to be linked to the cell cycle because (a) the periodicity corresponded to a fraction of the generation time and (b) the oscillations were accompanied by a transient increase in the budding index, mobilization of storage carbohydrates, and fermentative activity. Moreover, these oscillations occurred in a range of specific growth rates between 0.04 and 0.15 h(-1). All these criteria were consistent with the cell-cycle-related metabolic oscillations observed in the same range of growth rates in glucose-limited continuous cultures. The second type were short-period respiratory oscillations, independent of the specific growth rate. Both types of oscillation were found to take place consecutively and/or simultaneously during batch culture on trehalose. In addition, mobilization of intracellular trehalose emerged as a key parameter for the sustainability of these autonomous oscillations as they were no longer observed in a mutant defective in neutral trehalase activity. We propose that batch culture on trehalose may be an excellent device for further investigation of the molecular mechanisms that underlie autonomous oscillations in yeast.