EFFECT OF THE DILUTION RATE ON THE MODE OF OSCILLATION IN CONTINUOUS CULTURES OF SACCHAROMYCES-CEREVISIAE

The growth properties of the asymmetric budding yeast Saccharomyces ce revisiae were analysed during spontaneous oscillations in continuous c ultures at varying dilution rates D. The length of the oscillation per iod changed between 1.4 and 14 h in response to the decrease of diluti on rate from 0.15 to 0.05 h(-1). The distribution of parent and daught er cells in the population was determined microscopically after staini ng the bud scars and DNA. Most of the data obtained fits a theoretical population balance model assuming two-classes of subpopulations and i nteger ratios between the generation times of both classes. Some data has to be described by an extended population model assuming there is one parent and two daughter cell classes. How changes of dilution rate may cause an accidental switch of the mode of oscillation is demonstr ated. Glucose consumption and metabolite production were measured off- line by enzymatic methods and gas exchange was monitored on-line. All these data of one period point to internal and external signals respon sible for the synchronisation of the cell cycle. (C) 1998 Elsevier Sci ence B.V. All rights reserved.