An apparatus allowing the continuous cultivation of bacterial populations in a constant, competitive environment. Bacteria compete for a limiting nutrient in the medium. The medium is slowly added to the culture, and used medium plus bacteria are siphoned off at the same rate. The concentration of the limiting nutrient in the fresh medium determines the density of the steady-state population, and the rate at which the medium is pumped into the chemostat determines the bacterial growth rate. In chemostat experiments, environmental variables can be changed, one by one, to ascertain how these affect natural selection, or the environment can be held constant and the differential fitness of two mutations can be evaluated.
Subjects: Genetics and Genomics — Chemistry.