Effect of sugars on salt reception in true slime mold Physarum polycephalum. Physicochemical interpretation of interaction between salt and sugar receptions

Substrate composition directs slime molds behavior

Cells, including unicellulars, are highly sensitive to external constraints from their environment. Amoeboid cells change their cell shape during locomotion and in response to external stimuli. Physarum polycephalum is a large multinucleated amoeboid cell that extends and develops pseudopods. In this paper, changes in cell behavior and shape were measured during the exploration of homogenous and non-homogenous environments that presented neutral, and nutritive and/or adverse substances. In the first place, we developed a fully automated image analysis method to measure quantitatively changes in both migration and shape. Then we measured various metrics that describe the area covered, the exploration dynamics, the migration rate and the slime mold shape. Our results show that: (1) Not only the nature, but also the spatial distribution of chemical substances affect the exploration behavior of slime molds; (2) Nutritive and adverse substances both slow down the exploration and prevent the formation of pseudopods; and (3) Slime mold placed in an adverse environment preferentially occupies previously explored areas rather than unexplored areas using mucus secretion as a buffer. Our results also show that slime molds migrate at a rate governed by the substrate up until they get within a critical distance to chemical substances.

Membrane biophysicsdf chemoreception and taxis in the plasmodium of physarum polycephalum

The threshold phenomena observed in chemoreception and taxis of the plasmodium of Physarum polycephalum were analyzed on the basis of physical chemistry. Various physicochemical concepts and rules, e.g. the Schulze-Hardy rule, the lyotropic number and the hydrophobic interactions, were shown to be applicable reasonably well to the physiological functions in Physarum. It was stressed that the structural change of the surface membrane induced by reception of chemical stimuli plays a decisive role in recognition and sensitivity to the external stimuli as well as the appearance of tactic movement in the amoeboid motility of Physarum.