Development of Respiratory Activity during the Cell Cycle of Schizosaccharomyces pombe 972 h-: Respiratory Oscillations and Heat Dissipation in Cultures Synchronized with 2#-Deoxyadenosine

Abstract

Rates of O2 uptake and heat dissipation were measured in cultures of S. pombe that was induced to divide synchronously by adding 2 mM-2''-deoxyadenosine and then removing the inhibitor after 4 h. Respiratory oscillations occurred during the last 1.5 h of treatment with deoxyadenosine and throughout the subsequent period of synchronous growth. Before completion of the first synchronous division 3 peaks of O2 uptake occurred, the 3rd peak being coincident with cell division. These peaks were less sensitive to the rate-stimulating effect of the uncoupler, carbonyl cyanide m-chlorophenylhydrazone, than were the troughs, so that in the presence of the uncoupler the oscillations were attenuated. In the absence of uncoupler, heat dissipation of the culture increased linearly during and after deoxyadenosine treatment, with sharp increases (approximate doublings) in the rate of dissipation occurring at intervals similar to the mean generation time of an exponential culture. Heat dissipation also increased continuously in samples removed from such a culture and incubated with the uncoupler. The possible modulation of O2 uptake rates by respiratory control, and the implications of linear increases in heat dissipation are discussed.