The effects of starvation and acidification on lag phase duration of surviving yeast cells

Starvation is one of the most common forms of stress experienced in the wild life. Such conditions associate the other forms of stress such as acid, heat, oxidation, and so on. Organisms acclimate to such stresses and acquire the stress tolerances, which often trade-off their growth rates. To investigate whether starvation and the associated stresses may cause the changes in the growth and the central carbon metabolism, we stock-cultured the yeast S. cerevisiae on YNB agar plates up to a month and subsequently cultured in YNB broth. The pH of the agar medium just under the yeast's colonies sharply dropped from 5.0 to 3.9 in the first day, eventually reached approximately 3.0, and the viability logarithmically decreased. The surviving cells accumulated cell damages that were measured as the prolonged LPDs (lag phase durations). We did not, however, observe the effects of long-term stock-cultivations on the measured phenotypes: growth rates, the carrying capacities, and the glycolytic oscillations that are the temporal dynamics of the central carbon metabolism. Our study revealed that the contribution of cell damages to the total delay in growth was 78%, and that LPDs are closely related to damage-recovery mechanisms.