Evaluation of fluorescent stains for visualizing extracellular DNA in biofilms

Here we determine an optimal technique for the visualization of extracellular DNA in bacterial biofilms using the fluorescent eDNA stain TOTO-1 and the counterstain SYTO 60. This technique allows for more sensitive eDNA visualization than other fluorescent staining methods currently in use. •We evaluate fluorescent stains for used imaging extracellular DNA in biofilms.•The popular eDNA stain DDAO produces inaccurate results due to penetration of cells.•The popular eDNA stain propidium iodide is accurate but not very sensitive.•The highest sensitivity and accurate staining was obtained with TOTO-1.