Effect of glucose concentration on antibiotic tolerance of wild-type E. coli K-12 biofilm cultures. Cultures were grown as biofilms for 6 hours before being transferred to antibiotic treatment plates for 24 hours. LB medium was supplemented with varying amounts of glucose indicated below each bar ranging from 0-10 g/L. Reported cfu/biofilm data was determined after treatment. Black bars = control, 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.