Fig. 2.

The V. fischeri C8-HSL AI antagonizes LuxR_ARM81ld. (A) Growth of ΔahyI Aeromonas sp. ARM81 carrying aTc-inducible xre_ARM81ld-luxR_ARM81ld in a medium lacking aTc (white; No induction), a medium containing aTc supplemented with the medium alone (gray), cell-free culture fluids from WT (3OC6-HSL⁺ and C8-HSL⁺; green), ΔluxI (3OC6-HSL⁻ and C8-HSL⁺; red), ΔainS (3OC6-HSL⁺ and C8-HSL⁻; cyan), or ΔluxI ΔainS (3OC6-HSL⁻ and C8-HSL⁻; orange) V. fischeri. (B) PsmORF_ARM81ld-lux expression from E. coli carrying aTc-inducible xre_ARM81ld-luxR_ARM81ld grown in a medium containing aTc supplemented with the medium alone, cell-free culture fluids from WT (3OC6-HSL⁺ and C8-HSL⁺) V. fischeri ΔluxI (3OC6-HSL⁻ and C8-HSL⁺) V. fischeri ΔainS (3OC6-HSL⁺ and C8-HSL⁻) V. fischeri ΔluxI ΔainS (3OC6-HSL⁻ and C8-HSL⁻) V. fischeri, or in a medium lacking aTc (No induction). (C) Growth of ΔahyI Aeromonas sp. ARM81 carrying aTc-inducible xre_ARM81ld-luxR_ARM81ld in a medium lacking aTc (white; No induction), the medium containing aTc supplemented with DMSO (gray), C4-HSL (purple), 3OC6-HSL (cyan) or C8-HSL (red). All HSLs were supplied at 20 µM. (D) PsmORF_ARM81ld-lux expression from E. coli carrying aTc-inducible xre_ARM81ld-luxR_ARM81ld grown in a medium containing aTc supplemented with DMSO, C4-HSL, 3OC6-HSL, C8-HSL, or in a medium lacking aTc (No induction). HSL concentrations as in (C). Data are represented as mean ± SD with n = 3 biological replicates. RLU as in Fig. 1B (B, D). aTc; 0.1 ng mL⁻¹ (A, C), 50 ng mL⁻¹ (B) and 25 ng mL⁻¹ (D).