Bacterial culture is a basic technique in both fundamental and applied microbiology.The excessive reagent consumption and laborious maintenance of bulk bioreactors for microbial culture have prompted the development of miniaturized on-chip bioreactors.With the minimal choice of two compartments (N=2) and discrete time,periodic dilution steps,we realize a microfluidic bioreactor that mimics macroscopic serial dilution transfer culture.This device supports automated, long-term microbial cultures with a nanoliter-scale working volume and real-time monitoring of microbial populations at single-cell resolution. The use of surfactant Tween20 suppresses the biofilm growth and enables the pure planktonic growth.