Population dynamics in ecosystems, such as extinction, coexistence, and oscillation, result from non-linear interactions among multiple species. To better understand such complex systems, we need to perform both theoretical analysis and experiments that can be easily manipulated to test model predictions. Here we show a synthetic predator-prey system in Escherichia coli using two ‘quorum sensing (QS)' modules. ‘Predator' cells expressing a killer protein survive only when they receive an acyl-homoserine lactone (AHL) signal emanating from ‘prey' cells, which activates an antidote protein in the predator cells. Conversely, at sufficiently high densities, the predator cells kill the prey cells by sending a different AHL signal that activates a killer protein carried by the prey cells. A mathematical model predicted that the system would generate oscillation in the densities of the two populations in a specific parameter space. Adopting oscillation as a signature of the predator-prey system, we adjusted key parameters for oscillation, including strength of killing and stability of the AHL signals. Long-term microchemostat culturing of the system showed damped and sustained oscillations according to the model prediction. Such a synthetic ecosystem will allow us to further investigate the dynamics of multi-species systems concerning important ecological and evolutionary topics, and may have the potential for addressing medical and environmental problems, particularly those induced by QS microbial communities.

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