Designing a Chemostat and Cell Culture Measurement Device for Undergraduate Labs*

Commercial chemostats are a useful tool in biophysics and systems biology research. Continuous culture environment controls the growth and behavior of microorganisms, and provides applications to drug discovery and testing, antibiotic resistance, and bioengineering. In addition to academic and industry research, the chemostat is an excellent device for undergraduate education in microbiology. Multiplexed chemostat arrays and commercial products available are intended for graduate use and above. However, there is no chemostat product accessible for undergraduate use in a lab setting. During the 2023 Vanderbilt REU in Physics, my research partner Ella Cereghino and I have constructed a low-resource model of a chemostat with built-in optical density (OD) measurements. This design includes a single-channel chemostat and OD device powered by simple arduino electronics. The model can operate a steady state culture of Escherichia Coli for at least 12 hours and records cell density at any given time. Cell density is measured by the signal a photodiode pin records from light passing through a culture vial. The device is connected to a desktop computer to display measurements every minute. This model is ideal as an educational tool to introduce undergraduate students to microbiology and continuous culture. Potential experiments with E. coli include studying antibiotic resistance, and cell growth and substrate uptake rates under four different substrates.