Figure 5
From: Real-time detection of viable microorganisms by intracellular phototautomerism
The detection limit of the RTV assay and comparison to DEAD/LIVE BacLight™. The detection limit was assessed for the salicylic acid dye of the RTV assay and the Syto9 and propidium iodide dyes of the DEAD/LIVE BacLight™ method [2] in the Infinite F500 Tecan microplate reader. Bars indicate the fluorescence intensities in arbitrary units at a range of cell concentrations. All assays were carried out with suspensions of Staphylococcus aureus bacteria diluted in physiological salt solution (PSS) ranging from 109 to 103 bacteria ml-1 and were performed 6 times on PSS in the absence of cells to determine the average and 2× the standard deviation of the blank signal, as indicated by the dashed lines. (A) Measurements on live cells in quadruplicate, 500 μM salicylic acid, pH 2, excitation wavelength, 280 nm; emission wavelength, 400 nm (B) Measurements on live cells in quadruplicate, 500 μM salicylic acid, pH 1, excitation wavelength, 280 nm; emission wavelength, 400 nm (C) Measurements on live cells in triplicate (signals at 109 bacteria ml-1 were omitted because of saturation), 10 μM Syto9 and 60 μM propidium iodide, pH 7 excitation wavelength, 485 nm; emission wavelength, 535 nm (D) Measurements on dead cells (heat-treated for 5 min at 95°C) in triplicate, 10 μM Syto9 and 60 μM propidium iodide, pH 7, excitation wavelength, 485 nm; emission wavelength, 612 nm.