In Dictyostelium, mutagenesis can be performed by electroporation of a linearized transformation vector along with high concentrations of a compatible restriction enzyme. This leads to integration of the plasmid into genomic sites of the enzyme with a frequency of about 500 per 107 cells. Transformed cell clones are grown on agar plates in association with Klebsiella aerogenes on which they feed and form colonies. When the bacterial food source is exhausted in the center of the colonies, the population of cells begins to develop into distinct multicellular aggregates, each of which continue through development to form mature fruiting bodies. Mutant phenotypes with aberrant morphology can be directly identified by observation while the expression pattern of marker genes is detected by the colony blot technique.