Oscillations of redox states in synchronously dividing cultures of Acanthamoeba castellanii and Schizosaccharomyces pombe

The redox state of the mitochondria of Acanthamoeba castellanii and Schizosaccharomycespombe was assessed with a flying-spot fluorometer (Chance et al. 1978. Am. J.Physiol. 235:H 809) that provides excitation appropriate for oxidized flavoprotein or reducedpyridine nucleotide. Fluorescence signals could be resolved from thin films of cultures thatwere only one cell deep. In both organisms anoxia was associated with an increased pyridinenucleotide and decreased flavoprotein fluorescence. The addition of mitochondrial uncouplingagents increased the flavoprotein fluorescence and the fluorometer was able to resolveuncoupler-sensitive and uncoupler-insensitive fractions of S. pombe cultures. In both synchronousand asynchronous cultures of A. castellanii and S. pombe the mitochondrial redox stateoscillates with a period of 4.5 ± 1.0 min. Oscillations with much longer period, of the order ofan hour, are observed in synchronous cultures and these oscillations correlate with similaroscillations in respiratory rate, uncoupler sensitivity, and adenine nucleotide pool sizes. Theresults are consistent with the hypothesis that synchronous cultures of A. castellanii and S.pombe oscillate between the ADP-limited (state 4) and ADP-sufficient (state 3) respiratorystates, i.e., exhibit in vivo respiratory control