Energy metabolic regulation of oscillatory contraction activity in Physarum polycephalum

The influence of inhibitors of respiration (KCN), glycolysis (2-deoxy-D-glucose alone or in combination with monoiodo-acetate) and anaerobic conditions (N2 or 95% N2 + 5% CO2), as well as the effect of application of appropriate substrates (D-glucose, sodium acetate, alpha-ketoglutarate and pyruvate) on contraction behavior (of plasmodia) of Physarum polycephalum was investigated under low intensity red-light illumination. Application of inhibitors of respiration or glycolysis leads to significantly different periods of the force oscillations (2.0 +/- 0.4 min and 4.1 +/- 0.5 min, in the presence of inhibitors of glycolysis and respiration, respectively). In both cases, the force amplitude of oscillations is diminished in comparison to undisturbed energy production. The persistence of oscillations in the presence of inhibitors of glycolysis seems to rule out an exclusively glycolytic origin of the force oscillations. A continuous production of ATP is necessary since a blockade of the energy production causes a cessation of the oscillations. Application of substrates for respiration in the presence of inhibitors of glycolysis leads to an increase in the force amplitude and a slight prolongation of the oscillation period. In contrast, an application of glucose in the presence of a respiration inhibitor has no effect on the force amplitude and period.