An apparatus suitable for making a designer disease is disclosed. The apparatus comprises first, second, and third containers, each having two sections, I and II, separated by a semipermeable material through which a microbe can pass but cells from target and non-target populations cannot pass, and an entrance and an exit to each section. The entrance to section I of the first and second containers are circulation entrances, the exits from section II of the first and second containers are circulation exits, and the entrance to and exit from section I of the third container is a circulation entrance and a circulation exit, respectively. Conduits form a loop by connecting the circulation exit of each container to the circulation entrance to another container. A pump moves fluid around the loop and microbes in the fluid are mutated. A method of making a designer disease using that apparatus is also disclosed.
