Population regulation in microbial consortia using dual feedback control

An ongoing area of study in synthetic biology has been the design and construction of synthetic circuits that maintain homeostasis at the population level. Here, we are interested in designing a synthetic control circuit that regulates the total cell population and the relative ratio between cell strains in a culture that contains two different cell strains. We have developed a dual feedback control strategy that uses two separate control loops to achieve the two control objectives respectively. We have implemented the strategy in a population regulation circuit where both the total population size and relative cell strain ratio can be set by reference signals. The circuit shows robustness and adaptation to perturbations in cell growth rate and changes in cell numbers. The control architecture is general and could apply to any organism for which synthetic biology tools for quorum sensing, comparison between outputs, and growth control are available.