Effect of AI-2 quorum sensing circuit gene deletions on antibiotic tolerance of E. coli biofilm cultures. Cells were grown as biofilms for 6 hours before being transferred to treatment plates for 24 hours. Reported cfu/biofilm data was determined after treatment. 7a) Cultures grown at 37°C on LB only medium. 7b) Cultures grown at 37°C on LB and 10 g/L glucose. ΔluxS mutant lacked gene for AI-2 synthesis, ΔlsrK mutant lacked gene for AI-2 phosphorylation, ΔlsrR mutant lacked gene for lsr operon repression, and ΔlsrF mutant lacked gene for AI-2 degradation. Black bars = control, dark gray bars = kanamycin (100 ug/ml) challenge, light gray bars = ampicillin (100 ug/ml) challenge. Number at the base of each bar denotes the number of independent replicates. cfu = colony forming unit.