The effect of proteases on plasmodium formation in Didymium iridis

Growth and differentiation of wild type amoebae of Physarum polycephalum in liquid culture

A method for growing wild type amoebal strains of Physarum polycephalum in two-membered liquid culture is presented. The medium is a simple buffered salts solution. We found that a minimal level of divalent cation was required for growth. All amoebal strains tried to date have grown under our conditions in stationary culture. Growth under gyratory conditions was only successful at 60 rpm or less and consistent growth required a period of adaptation over several transfers. Differentiation of two apogamic strains, CL and CH1, were compared. Contrary to the results seen on agar plates, the time of onset for the first committed amoebae was identical for both strains in liquid culture. Attempts to demonstrate mating between two genetically compatible amoebal strains grown together in liquid culture were not successful.

Analysis of an inducer of the amoebal-plasmodial transition in the myxomycetes Didymium iridis and Physarum polycephalum

Recent studies with amoebae of the Myxomycetes Didymium iridis and Physarum polycephalum reveal that competence to undergo sexual fusion or to differentiate to plasmodia apogamically can be induced by a diffusible factor. Suspension cultures of Didymium amoebae have proven to be a good source of the inducer activity. Cell-free culture supernatants accelerated mating of Didymium and Physarum amoebae and also apogamic differentiation of the Physarum strain Colonia . Characterization and purification of the inducer activity is being conducted with a semiquantitative bioassay based on the induction of zygote formation in suspensions of mating-compatible Didymium amoebae.