Direct transfer of coliphage lambda DNA from Escherichia coli to cellular slime mold Dictyostelium discoideum

Dictyostelium discoideum myxamoebae were cultured with Escherichia coli cells infected with lambda phage in the presence of chloramphenicol. After eliminating the uningested bacteria by repeated centrifugation in a Percoll gradient, we examined the myxamoeba cytoplasm (not the food vacuole) for the presence of phage DNA. A significant amount of DNA extracted from the myxamoebae was hybridizable with purified phage lambda DNA, and capable of forming phage particles when packaged in vitro with phage lambda proteins. The EcoRI restriction maps of the phages recovered from the plaques were identical to that of the infecting phage. These results strongly suggest that phage DNA molecules were taken up by the cellular slime mold cells and that at least some fraction existed in intact form.