Dictyostelium discoideum are non-pathogenic amoebae that live in the soil and prey on bacteria. When starved, the individual cells aggregate into centers that contain about 50,000 cells. This is one of the best genetic systems to study the role of allorecognition in development and in social cooperation. The video shows two strains of D. discoideum that differ in two genes, tgrB1 and tgrC1, which are responsible for allorecognition in this organism. On the left, the red-labeled and green-labeled cells carry compatible alleles of tgrB1 and tgrC1. These cells enter the aggregates and remain mixed throughout development. On the right, the red-labeled and green-labeled cells carry incompatible alleles of tgrB1 and tgrC1. They initially aggregate together but then they segregate and fail to cooperate. This video is from the research of Dr. Gad Shaulsky.