Behaviour of Dictyostelium discoideum amoebae and Escherichia coli grown together in chemostat culture.

When Dictyostelium discoideum amoebae and Escherichia coli were grown together in chemostat culture damped oscillations in the population densities of the organisms occurred followed by a sudden increase in bacterial numbers and a concommitant decrease in the number of amoebae. After the system had come to equilibrium altering the dilution rate resulted in a monotonic change in the experimental variables to new steady state levels. A square wave increase in the concentration of limiting nutrient in the feed medium during the oscillatory phase of culture produced a sinusoidal response indistinguishable from that prior to the perturbation. The results are more complicated than those predicted by simple models of microbial predator-prey dynamics although they correspond most nearly to models which incorporate saturation kinetics.