FIGURE 7.

Response of the diacetyl-biosensors to diacetyl-producer supernantants. (A,B) Single-cell fluorescence measurements by flow cytometry, in the absence (gray) and presence (green) of supernatant L. lactis subsp. lactis biovar diacetylactis MR3-T7 grown in M17 or skim milk, respectively. (C) Single-cell fluorescence measurements by flow cytometry, in the absence (gray) and presence of diacetyl solution 0.42 mM (green). Note that diacetyl at a concentration 0.42 is used because the M17 supernatant contains diacetyl at the same concentration. Fluorescence measurements were taken at the beginning of stationary growth phase. 10,000 ungated events for each sample are shown.