Use of a Fluorescence-Based Assay To Measure Escherichia coli Membrane Potential Changes in High Throughput

Abstract

Bacterial membrane potential is difficult to measure using classical electrophysiology techniques due to the small cell size and the presence of the peptidoglycan cell wall. Instead, chemical probes are often used to study membrane potential changes under conditions of interest. Many of these probes are fluorescent molecules that accumulate in a charge-dependent manner, and the resulting fluorescence change can be analyzed via flow cytometry or using a fluorescence microplate reader. Although this technique works well in many Gram-positive bacteria, it generates fairly low signal-to-noise ratios in Gram-negative bacteria due to dye exclusion by the outer membrane.