Temperature dependence of the O2-oscillation pattern in the filamentous cyanobacterium Oscillatoria chalybea and in Chlorella kessleri.

Five characteristic discontinuities of the pattern of oxygen evolution have been detected for the filamentous cyanobacterium Oscillatoria chalybea in the temperature range of 0 degree C to 30 degrees C. The temperatures at which these discontinuities occur are: approximately 5 degrees C, approximately 11 degrees C, approximately 15 degrees C, approximately 21 degrees C and approximately 25 degrees C. The calculated initial 5-S state distribution, the miss parameter and the fraction of the fast transition S3-->So + O2 are affected. The discontinuities are observed at the same transition temperature also for Chlorella kessleri hence are not specific for the cyanobacterium. Based on these studies it is concluded that the not vanishing oxygen signal under the first flash of a flash train in Oscillatoria cannot have its origin in interactions between oxygen-evolving complexes. A decrease of temperature should slow down the expected charge exchanges, improve the oscillations thus reduce or lower the first two oxygen amplitudes of the oscillatoria pattern. Lowering of the temperature improves the oscillations but does not lower the first O2 signal of the pattern.