Biofilms grown in chamber slides were stained by removing
conditioned medium from the wells through gentle aspiration,
followed by the addition of Hv-starve staining solution
(same volume as medium used to grow biofilm, e.g. 500 μl)
for 60 min at room temperature in the dark. Staining solution
was then removed, the surface was gently washed
once with the addition and subsequent removal of another
equal volume of Hv-starve, and fresh Hv-starve
was added, followed by direct visualization.