Background:Multiplexed milliliter-scale chemostats are useful for measuring cell physiology under various degrees of nutrient limitation and for carrying out evolution experiments.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,precision,and operational range of flow rate — are not explicitly characterized.Methods:Here we re-purpose a published multiplexed culturing device to develop a multiplexed milliliter-scale chemostat.Flow rates for eight chambers can be independently controlled to a wide range,corresponding to population doubling times of 3～13 h,without the use of expensive feedback systems.Results:Flow rates are precise,with the maximal coefficient of variation among eight chambers being less than 3％.Flow rates are accurate,with average flow rates being only slightly below targets,i.e.,3％-6％ for 13-h and 0.6％-1.0％ for 3-h 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.Conclusions:We achieve precise control of cellular growth in a low-cost milliliter-scale chemostat array,and show that the achieved precision reduces the error when measuring biological processes.