Cellular Interaction in Plasmodial Slime Moulds

Abstract

During this century progress in biology has been greatly facilitated by the use of model organisms which may be relatively unimportant in nature but which are good systems for the study of specific problems. The interaction between genetically different cells is a fundamental biological problem (e.g. transplantation of organs, blood transfusion, grafting of plants), and an excellent model organism for studying such problems is the myxomycete Physarum polycephalum, which can be grown rapidly on simple media in the laboratory; biochemical and genetical work on P. polycephalum has been carried out in many laboratories. Genetical work has also been carried out with a second species, Didymium iridis, which, however, has not been grown in pure culture on soluble media and therefore is less suitable for physiological and biochemical investigations. The life cycle and features of myxomycetes have been described extensively (AShworth and DEe 1975, COllins and BEtterley 1982, DEe 1982, GOodman 1980, HAugli etal. 1980, LAne 1981, and OLive 1975). A brief description of the life cycle follows and is summarized in Fig. 1. The Plasmodium, a mass of protoplasm containing up to several million nuclei, is not subdivided into cells and is surrounded by a plasma membrane and slime. The lack of the rigid outer wall gives the Plasmodium a high flexibility, which is unique for such large cells. Starvation of a Plasmodium may give rise to a sclerotium, a resting phase, which under suitable conditions will produce a Plasmodium again.