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Chemosensors 2018, 6(2), 21; https://doi.org/10.3390/chemosensors6020021

Using Fluorescence Intensity of Enhanced Green Fluorescent Protein to Quantify Pseudomonas aeruginosa

1
Department of Chemistry, Westminster College, New Wilmington, PA 16172, USA
2
Departments of Chemistry, Doane University, Crete, NE 68333, USA
*
Authors to whom correspondence should be addressed.
Received: 30 March 2018 / Revised: 25 April 2018 / Accepted: 27 April 2018 / Published: 3 May 2018
(This article belongs to the Special Issue Fluorescent Probes for Live Cell Imaging)
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Abstract

A variety of direct and indirect methods have been used to quantify planktonic and biofilm bacterial cells. Direct counting methods to determine the total number of cells include plate counts, microscopic cell counts, Coulter cell counting, flow cytometry, and fluorescence microscopy. However, indirect methods are often used to supplement direct cell counting, as they are often more convenient, less time-consuming, and require less material, while providing a number that can be related to the direct cell count. Herein, an indirect method is presented that uses fluorescence emission intensity as a proxy marker for studying bacterial accumulation. A clinical strain of Pseudomonas aeruginosa was genetically modified to express a green fluorescent protein (PA14/EGFP). The fluorescence intensity of EGFP in live cells was used as an indirect measure of live cell density, and was compared with the traditional cell counting methods of optical density (OD600) and plate counting (colony-forming units (CFUs)). While both OD600 and CFUs are well-established methods, the use of fluorescence spectroscopy to quantify bacteria is less common. This study demonstrates that EGFP intensity is a convenient reporter for bacterial quantification. In addition, we demonstrate the potential for fluorescence spectroscopy to be used to measure the quantity of PA14/EGFP biofilms, which have important human health implications due to their antimicrobial resistance. Therefore, fluorescence spectroscopy could serve as an alternative or complementary quick assay to quantify bacteria in planktonic cultures and biofilms. View Full-Text
Keywords: Pseudomonas aeruginosa; enhanced green fluorescent protein; fluorescence spectroscopy; bacterial quantification; biofilms; fluorescent probe Pseudomonas aeruginosa; enhanced green fluorescent protein; fluorescence spectroscopy; bacterial quantification; biofilms; fluorescent probe
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Wilson, E.; Okuom, M.; Kyes, N.; Mayfield, D.; Wilson, C.; Sabatka, D.; Sandoval, J.; Foote, J.R.; Kangas, M.J.; Holmes, A.E.; Sutlief, A.L. Using Fluorescence Intensity of Enhanced Green Fluorescent Protein to Quantify Pseudomonas aeruginosa. Chemosensors 2018, 6, 21.

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