Cell-conditioned medium (CM) induces the dispersal of microcolonies.

<p>(A) Schematic drawing of the experimental set-up. Confluent FaDu cells were washed and incubated with DMEM. After 5 h, the CM was collected, sterile filtered, and added at a 1:1 volume ratio to bacterial meningococcal suspensions where microcolonies had been allowed to form for 3 h (initial bacterial concentration of 10⁷ CFU/ml). A black horizontal line in panels B and D represents the 3 h time point. Bacteria were observed by live-cell time-lapse microscopy. DMEM was used as a control. (B) Microcolony dispersal upon addition of CM from infected (+) or uninfected (-) cells to FAM20 bacteria in liquid. (C) Microcolony dispersal was examined by live-cell time-lapse microscopy after addition of CM. Representative images are shown 10, 20 and 30 min after induction. Scale bar, 10 μm. (D) Microcolony dispersal upon addition of CM collected from FaDu cells after 5, 15, and 30 min and 1 h and 5 h. (E) Microcolony dispersal of FAM20 resuspended (10⁷ CFU/ml) in either CM or DMEM (control) when the incubation was initiated. Data represent the mean ± SD of three independent experiments. ^*p < 0.05. ns, non-significant.