Developing a low-cost milliliter-scale chemostat array for precise control of cellular growth

Multiplexed milliliter-scale chemostats are useful for measuring cell physiology under various degrees of nutrient limitation and for experimental evolution. In each chemostat, fresh medium containing a growth rate-limiting metabolite is pumped into the culturing chamber at a constant rate, while culture effluent exits at an equal rate. Although such devices have been developed by various labs, key parameters - the accuracy and precision of flow rate and the operational range - are not explicitly characterized. Here we report the development of multiplexed milliliter-scale chemostats where flow rates for eight chambers can be independently controlled to vary within a wide range, corresponding to population doubling times of 3~ 13 hours. Importantly, flow rates are precise and accurate without the use of expensive feedback systems. Among the eight chambers, the maximal coefficient of variation in flow rate is less than 3%, and average flow rates are only slightly below targets, i.e., 3-6% for 13-hour and 0.6-1.0% for 3-hour doubling times. This deficit is largely due to evaporation and should be correctable. We experimentally demonstrate that our device allows accurate and precise quantification of population phenotypes.