Ergot Alkaloids Affect Foraging Activity of the Slime Mold Physarum polycephalum

We tested whether ergot alkaloids would affect the interaction of a protist with an ergot alkaloid-producing fungus by studying the response of the plasmodial slime mold Physarum polycephalum to cultures of Aspergillus leporis. Ergot alkaloid profiles were manipulated by culturing A. leporis and its easD knockout derivative on media for 6 or 13 days. Six-day-old, wild-type A. leporis samples contained abundant lysergic acid α-hydroxyethylamide (LAH) that was greatly depleted by 13 days. The intermediate chanoclavine-I was the predominant ergot alkaloid in all samples of the easD knockout. Inoculum of P. polycephalum was placed equidistant between the fungus-colonized agar medium explant, and the preference of the slime mold for either fungal explant was observed. When offered 6-day-old samples of wild-type A. leporis (containing mainly LAH) or the easD knockout (containing mainly chanoclavine-I), plasmodia of P. polycephalum preferred the easD knockout strain over wild type by a significant margin (p = 0.0002). When given the same options at 13 days, there was no longer a preference for the easD knockout over wild type, which by that time had lost more than 90% of its LAH. Our data demonstrate that ergot alkaloids, including LAH and chanoclavine-I, affect the interaction of P. polycephalum with A. leporis.