Fig. 1. The structure of endosomes can be modulated by culture conditions in Dictyostelium cells. Dictyostelium cells were grown for 3 days in the presence of E. coli bacteria (A) or in HL5 medium (B) and processed for electron microscopy. (C) Cells grown in HL5 medium were incubated for 2 hours in the presence of U18 before fixation. Each image shows a typical endosome in the indicated condition. Bars, 0.5 µm.