The axenic mutations and endocytosis in Dictyostelium.

The axenic mutations of Dictyostelium offer a unique opportunity to explore the relationship between phagocytosis and pinocytosis and to examine the mechanism by which a cell shifts from one mode of feeding to the other. The axenic mutations also provide a means of exploring the relationships between endocytosis and other forms of cell motility. This chapter has described the known mutations that affect axenic growth, methods for culturing wild-type and axenic cells and measuring their growth, and methods for monitoring the effects of the axenic mutations on endocytosis and cell movement. The importance has been emphasized of distinguishing effects of the axenic genotype that are expressed constitutively (i.e., during growth on either bacteria or liquid medium) from those that are a function of axenic growth conditions. The methods described in this chapter, applied to wild-type cells and to cells carrying a full complement of the axenic mutations, have shown that the axenic mutations have constitutive effects on cell-substratum interactions, and inducible effects on cell locomotion and pinocytosis.