Fig. 4. Short-range communication regulates horizontal gene transfer.

Quorum-sensing systems of a phage system (φ3T) and b integrative conjugative element (ICEBs1). From top to bottom: scheme of quorum-sensing system, distribution of signal producers (blue outlines) and receivers (red outlines) and their reporter expression, GFP expression for φ3T system (artificially colored yellow), and YFP expression for ICEBs1 system (scale bar = 10 μm), and reporter expression as a function of the distance of cells to the boundary of signal producers. Reporter gene expression indicates induction of horizontal gene transfer: lytic lifestyle for phage system and conjugation for ICEBs1 element. Black line marks best-fit curves (see “Methods”). The zone of inhibition is determined by the spatial distance from the boundary of signal producers, where we observe repression in reporter gene expression (Supplementary Fig. 19). c Representative microscopy image of coculture of ΔconB ICEBs1 donor cells (blue outline) and uninfected recipient cells (red outline) (scale bar = 10  μm). Donor cells that express YFP induce conjugation. d Induction probability as a function of fraction of uninfected recipient cells in the local neighborhood ($n=\mathrm{89,\; 292}$ cells; numbers above bars in plot show how cells are distributed across neighborhoods). Neighborhood size is determined by the zone of inhibition. Induction probability increases significantly with fraction of uninfected recipient cells in the local neighborhood (regression: $y=\frac{1}{1+e^{a\left(x+b\right)}};a=-4.7\pm 0.2\left(\mathrm{s}.\mathrm{e}.\right),p_a<{10}^{-9};b=-1.1\pm 0.01,p_b<{10}^{-14}$; $\mathrm{residual}\mathrm{s}.\mathrm{e}.=0.01;\mathrm{d.f.}=9$). Source data are provided in Supplementary Data 1.