Fig. 6.

Calculated 3OC6HSL concentration predicts GFP expression. (A) The fraction of colonies (n = 84,213) that expressed GFP was greater (more red) at high densities (Top) and short radial distances (Left). (B) Compared with an uninduced colony (B, i, red), a target colony was more likely to express GFP (green) if (B, ii) it was surrounded by more source colonies (blue) or (B, iii) the distance to source colonies was shorter. (C) The fraction of expressing colonies and the predicted probability of induction (α), were lower for colonies with lower calculated concentrations of 3OC6HSL (P < 1 × 10⁻¹⁵). The critical 3OC6HSL concentration (C_crit) was ${\overline{C}}_t$ = 0.38. (D) The predicted fraction of expressing colonies, α, was higher at high density and low average radial distance, matching colony measurements in tumor sections (A). (E and F) Predicted α-fractions were lower at longer average radial distances (E) and higher at higher densities (F). Numbers to the right are density (×10¹⁰ cfu/g) for E and G, and radius (µm) for F, H, and I. (G and H) The predicted 3OC6HSL concentration at target colonies (${\overline{C}}_t$) was lower at higher average radial distances (G), and higher at higher densities (H). (I) Expanded range of H. At low densities below ρ_crit = 0.11 × 10¹⁰ cfu/g, the predicted 3OC6HSL concentration was zero. At the maximum possible bacterial density in liver (ρ_liv = 0.00792 × 10¹⁰ cfu/g), no 3OC6HSL was produced, regardless of spatial distribution.