FIG 4.

CAI-1 is delivered via OMVs to nonproducing cells and triggers intracellular QS activation. The membrane of CAI-1-containing OMVs (OMV-producing strain MR17 [ΔluxM ΔluxS]) was fluorescently stained, and green fluorescent OMVs were detected by the microscope (top panel). These OMVs were incubated with the nonfluorescent reporter strain V. harveyi NL20 (AI⁻ cqsS⁺ ΔluxN ΔluxPQ P_luxC-mCherry). At the indicated times, cells were analyzed by microscopy for green fluorescence and expression of the P_luxC-mCherry reporter fusion (bottom panels). PH, phase-contrast images; green fluorescence, green fluorescence images; mCherry, red fluorescence images. Bar, 5 μm.