[Yeast growth under alternating temperature conditions and the possibility of originating thermotolerant forms]

Abstract

The chemostat culture of Candida utilis was grown under the conditions of varying temperatures: one generation grew at an optimal temperature of 31 degrees C, the second at supraoptimal temperatures: either 35, 36 or 37 degrees C; these were alternated during 6-8 generations. Changes in the growth yield were studied as well as changes in the content of protein, RNA and DNA in cells and changes in the zeta-potential of cells at a growth rate of 0.34 hr-1. At this rate, the population became "synchronous-like" and contained up to 60% of simultaneously budding cells. When the temperature of cultivation was periodically changed, the content of RNA and DNA in the biomass fluctuated at a decreasing amplitude around values found during the growth at the optimal temperature; the electro-kinetic characteristics of cells were also in the attenuated oscillating state approaching the norm. The authors discuss how the population retains the value of growth yield constant when it is grown under the conditions of varying temperatures and what is the origin of thermotolerant forms.