Kinetic analysis of dye reduction profiles provide deeper insights into the electron transfer activity of bacterial...

The Dye Reduction-based Electron-transfer Activity Monitoring (DREAM) assay offers a rapid, scalable, and culture-independent method for assessing bacterial respiratory activity. In this study, we have developed and applied a kinetic framework to extract six quantitative metrics from DREAM assay absorbance-time profiles: two derived from raw absorbance data - Dye-reduction Quotient (DQ) and Maximal Slope Interval (MSI) - and four from inverse-sigmoidal curve fitting - Baseline Absorbance (BA), Reduction Amplitude (RA), Time of Maximum Kinetic Shift (TMKS), and Redox Completion Index (RCI). These metrics complement traditional bacterial count methods by offering functional insights into metabolic activity, though they must be interpreted in a comparative rather than absolute context. We have applied this framework to two experimental conditions with mixed bacterial cultures, viz., varying bacterial concentrations and different substrate environments, to demonstrate how these metrics collectively capture the magnitude, timing, and dynamics of electron transfer processes in practical situations. This comprehensive kinetic quantification enhances the interpretive power of the DREAM assay and broadens its applicability for evaluating microbial performance in the bioprocessing and biotechnology industry and in environmental samples.