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

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.

Graphical abstract

Keywords

chemostats / microbes / evolution / physiology / multiplex

References

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SUPPLEMENTARY MATERIALS

The supplementary materials can be found online with this article at http://doi.org/1007/s40484-018-0143-8

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.

COMPLIANCE WITH ETHICS GUIDELINES

The authors David Skelding, Samuel F M Hart, Thejas Vidyasagar, Alexander E Pozhitkov and Wenying Shou declare that they have no conflict of interests.ƒThis article does not contain any studies with human or animal subjects performed by any of the authors.

RIGHTS & PERMISSIONS

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