Abstract
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.
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Acknowledgements
We thank Jean-Paul Toussaint and Chris Takahashi for their help in the initial fabrication and assembly of the turbidostat array, and Kennan Mell for testing and help with software implementation. We thank Chris Takahashi and past and current members of the Shou Lab (Justin Burton, Robin Green, Li Xie, and Alex Yuan) for productive discussions of this project. This work is funded by the NIH, the W.M. Keck foundation, and Fred Hutch Cancer Research Center.
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Author summary: Chemostats are useful devices for examining cell physiology and evolution, because they maintain a population of cells at a controlled reproduction rate and cell density in a fixed volume. We have improved an existing culturing device to be run as a multi-plexed chemostat that maintains eight separate populations at independently-controlled reproduction rates with high precision and accuracy. We present experimental results showing that the precision reduces the error in measuring properties of a population of yeast cells.
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Skelding, D., Hart, S.F.M., Vidyasagar, T. et al. Developing a low-cost milliliter-scale chemostat array for precise control of cellular growth. Quant Biol 6, 129–141 (2018). https://doi.org/10.1007/s40484-018-0143-8
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DOI: https://doi.org/10.1007/s40484-018-0143-8