Patterns in the distribution of intracellular ATP concentration in relation to coordination of amoeboid cell behavior in Physarum polycephalum.

The Physarum plasmodium reacts tactically to external stimuli. The cell behavior of this giant amoeboid cell was studied by analysing intracellular ATP concentration. The two-dimensional (2D) spatial distribution of ATP depended on cell shape: a polar pattern for a unidirectionally migrating plasmodium, a bowl shape for a circular plasmodium, a hump shape for an oval plasmodium, or a wavy pattern for plasmodia stimulated with blue light or confined in a small chamber, etc. Local external stimulation brought about new patterns of ATP distribution. The ATP concentrations around the stimulated frontal region were reduced by about a half stimulation with KCl (repellent) or casamino acids (attractant). In both cases, migration was inhibited. Migration velocity increased almost linearly with increasing concentration of intracellular ATP above the threshold (about 20 micrograms/mg protein). Under anaerobic conditions or at low temperatures, the intracellular ATP oscillated slowly with a periodicity of about 30 min. Pattern formations in the intracellular ATP concentration and amoeboid coordination are discussed in terms of coupled chemical oscillators in a self-organizing system.