Figure 2

In situ detection of metabolic activity and microenvironmental conditions in a dental biofilm outside the mouth. Microsensors were used to measure concentration profiles of NO₃^-, O₂, NO, N₂O and pH in dental plaque. The medium contained a non-buffered mineral mix and 2% sucrose. The upper panels (a-d) show measurements with 50 μM NaNO₃ (open red symbols) in the overlying medium. The lower panels (e-h) show measurements in the absence of NaNO₃ (black symbols) and in the presence of 760 μM NaNO₃ (red and green symbols). Measurements depicted by the green symbols were performed in the presence of phosphate-buffered saline (pH 7.2) and 760 μM NaNO₃. The horizontal line represents the biofilm surface. Measurements were done in the same sample spot and thus are directly comparable.