Figure 4. Expression of agr P₃ promoter in biofilms after AIP addition.

Dual-labeled biofilms (P_sarA-RFP, P_agrP3-GFP) were grown for 2 days, and AIP-I (50 nM final) was added to the growth media. Biofilm integrity and RFP/GFP fluorescence were monitored with CLSM at day 3 and 4. Greenish yellow color indicates expression of the agr P₃-GFP reporter (pDB59). (A) Addition of AIP-I to an agr type I wild type strain (AH596) or (B) agr deficient strain (AH861). (C) Addition of interfering AIP-II to an agr type-I strain biofilm (AH596). CLSM image reconstructions are representative of three separate experiments and each side of a grid square represents 20 µM.