Low-Cost Clamp-On Photometers (ClampOD) and Tube Photometers (TubeOD) for Online Cell Density Determination

Optical density (OD) measurement is the gold standard to estimate microbial cell density in aqueous systems. Recording microbial growth curves is essential to assess substrate utilization, gauge sensitivity to inhibitors or toxins, or determine the perfect sampling point. Manual sampling for cuvette...

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Bibliographic Details
Published in:	Frontiers in microbiology Vol. 12; p. 790576
Main Authors:	Deutzmann, Jörg S, Callander, Grace, Gu, Wenyu, Müller, Albert L, McCully, Alexandra L, Ahn, Jenna Kim, Kracke, Frauke, Spormann, Alfred M
Format:	Journal Article
Language:	English
Published:	Switzerland Frontiers Media S.A 13-01-2022
Subjects:	anaerobic growth monitoring continuous cell density measurement low-cost Microbiology online growth recording online thermophilic growth monitoring photometer online thermophilic growth monitoring low-cost photometer online growth recording continuous cell density measurement anaerobic growth monitoring
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Summary:	Optical density (OD) measurement is the gold standard to estimate microbial cell density in aqueous systems. Recording microbial growth curves is essential to assess substrate utilization, gauge sensitivity to inhibitors or toxins, or determine the perfect sampling point. Manual sampling for cuvette-photometer-based measurements can cause disturbances and impact growth, especially for strictly anaerobic or thermophilic microbes. For slow growing microbes, manual sampling can cause data gaps that complicate analysis. Online OD measurement systems provide a solution, but are often expensive and ill-suited for applications such as monitoring microbial growth in custom or larger anaerobic vessels. Furthermore, growth measurements of thermophilic cultures are limited by the heat sensitivity of complex electronics. Here, we present two simple, low-cost, self-assembled photometers-a "TubeOD" for online measurement of anaerobic and thermophilic cultures in Hungate tubes and a "ClampOD" that can be attached to virtually any transparent growth vessel. Both OD-meters can be calibrated in minutes. We detail the manufacturing and calibration procedure and demonstrate continuous acquisition of high quality cell density data of a variety of microbes, including strict anaerobes, a thermophile, and gas-utilizing strains in various glassware. When calibrated and operated within their detection limits (ca. 0.3-90% of the photosensor voltage range), these self-build OD-meters can be used for continuous measurement of microbial growth in a variety of applications, thereby, simplifying and enhancing everyday lab operations.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 Edited by: Frank Schreiber, Federal Institute for Materials Research and Testing (BAM), Germany Reviewed by: Thomas Egli, ETH Zürich, Switzerland; Thomas Maskow, Helmholtz Centre for Environmental Research, Helmholtz Association of German Research Centres (HZ), Germany This article was submitted to Microbial Physiology and Metabolism, a section of the journal Frontiers in Microbiology
ISSN:	1664-302X 1664-302X
DOI:	10.3389/fmicb.2021.790576