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Updated: Jan 31, 2026

Assessment of DNase Activity by Ratiometric Fluorescence Resonance Energy Transfer
Published on: July 25, 2025
Use of Ratiometric Probes with a Spectrofluorometer for Bacterial Viability Measurement
Jérôme Cléach1,2,3,4,5, Denis Watier1, Bruno Le Fur6
1Université Littoral Côte d'Opale, EA 7394 - ICV - Institut Charles Viollette, USC ANSES - ULCO, F-62200 Boulogne-sur-Mer, France.
Abstract:
Assessment of microorganism viability is useful in many industrial fields. A large number of methods associated with the use of fluorescent probes have been developed, including fluorimetry, fluorescence microscopy, and cytometry. In this study, a microvolume spectrofluorometer was used to measure the membrane potential variations of Escherichia coli. In order to estimate the sensitivity of the device, the membrane potential of E. coli was artificially disrupted using an ionophore agent: carbonyl cyanide 3-chlorophenylhydrazone. The membrane potential was evaluated using two ratiometric methods: a Rhodamine 123/4',6-diamidino-2-phenylindole combination and a JC-10 ratiometric probe. These methods were used to study the impact of freezing on E. coli, and were compared with the conventional enumeration method. The results showed that it was beneficial to use this compact, easy-to-use, and inexpensive spectrofluorometer to assess the viability of bacterial cells via their membrane potential.
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