Temperature-compensated ultradian variation in cellular protein content of Acanthamoeba castellanii revisited.

Synchronous cultures of the soil amoeba Acanthamoeba castellanii, established in the laboratory by selection procedures, show oscillations of total cell protein, as well as respiration. Previously, time series analysis by Aspect, a University of Warwick Computer Unit Program, showed an average period of 76 min. A reanalysis by least-squares rhythmometry revealed that, in general, the analyses accompanying the original paper and those in this replication agree very well. The periods extracted by the two approaches differ by only 1 to 5 min. In one case, when the original analysis did not detect a statistically significant period, however, the analysis used here does so. While the incubation temperatures used varied from 20 to 30 degrees C and cell division time increased from 7.8 hr at 30 degrees C to 16 hr at 20 degrees C, the metabolic bioperiodicity appeared to be temperature compensated. Decimation studies indicate that the sampling interval of 5 to 15 min must not be further reduced. It is promising to incorporate the study of ultradian metabolic rhythms into a broad spectral approach, i.e., for a concomitant assessment of ultradian, circadian, and infradian rhythms.