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Significance Statement
Stable and reproducible growth conditions are particularly important when trying to decipher the precise mechanisms of cell functioning. Continuous culture devices constitute the best means to establish such conditions and reaching a physiological steady state in cell populations, which reduce interference or noise arising from a constantly fluctuating environment. However, the use of continuous culture is not common, which is not surprising since commercially available continuous culture instruments are expensive, rarely customizable, and not designed to handle small volumes. To address this issue, we have conceived and built the Versatile Continuous Culture Device (VCCD), an affordable, open-source, and highly-customizable instrument that can execute different types of continuous culture experiments. We provide users with detailed instructions on how to use and adapt the Versatile Continuous Culture Device for different needs, as well as a robust and user-friendly graphical user interface. We believe that the Versatile Continuous Culture Device can become a reference for continuous culture instruments, and a starting point for the creation of an open-source small-scale bioreactor.
Figure Legend: Hardware configuration of the Versatile Continuous Culture Device (VCCD) and schematic depiction of culture-refreshing steps.
(A) Three-dimensional representation of the Versatile Continuous Culture Device. The system consists of three independently controlled continuous culture units supported by a plexiglass acrylic structure. For each unit, transmittance is measured through the culture chamber by a light-emitting diode coupled to a photo receiver and then reported to a user interface control system. The culture refreshing capability is provided by computer-controlled pinch valves that manage air and liquid flows inside each culture unit. (B) First step of a culture refresh cycle (culture dilution). Upon pinch valve activation, two tubes of the culture unit get pinched, and the air flow is diverted to the medium bottle resulting in the addition of medium into the culture tube. (C) Second step of a culture refresh cycle (excess culture removal). By returning the pinch valve to its original position, two tubes of the culture unit are pinched, which then redirects the air flow to the culture tube and causes the excess of volume to be evacuated into the trash bottle.
Journal Reference
PLoS One. 2015 Jul 21;10(7):e0133384.
Matteau D1, Baby V1, Pelletier S2, Rodrigue S1.
[expand title=”Show Affiliations”]1Département de biologie, Université de Sherbrooke, Sherbrooke, Québec, Canada.
2Département de physique, Université de Sherbrooke, Sherbrooke, Québec, Canada.
[/expand]Abstract
BACKGROUND:
Continuous culture devices can be used for various purposes such as establishing reproducible growth conditions or maintaining cell populations under a constant environment for long periods. However, commercially available instruments are expensive, were not designed to handle small volumes in the milliliter range, and can lack the flexibility required for the diverse experimental needs found in several laboratories.
METHODOLOGY/PRINCIPAL FINDINGS:
We developed a versatile continuous culture system and provide detailed instructions as well as a graphical user interface software for potential users to assemble and operate their own instrument. Three culture chambers can be controlled simultaneously with the proposed configuration, and all components are readily available from various sources. We demonstrate that our continuous culture device can be used under different modes, and can easily be programmed to behave either as a turbidostat or chemostat. Addition of fresh medium to the culture vessel can be controlled by a real-time feedback loop or simply calibrated to deliver a defined volume. Furthermore, the selected light-emitting diode and photodetector enable the use of phenol red as a pH indicator, which can be used to indirectly monitor the bulk metabolic activity of a cell population rather than the turbidity.
CONCLUSIONS/SIGNIFICANCE:
This affordable and customizable system will constitute a useful tool in many areas of biology such as microbial ecology as well as systems and synthetic biology.
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