Exposure to sub-inhibitory concentrations of norfloxacin induces the lytic cycle of three LES phages. Mid-exponential phase LESB58 cultures (OD600 0.5) were exposed to sub-inhibitory norfloxacin (50 ug ml-1) for 30 and 60 min before recovery for 2 h and total DNA extraction. Total phage vs prophage numbers were quantified by Q-PCR with SYBR green and specific primers. Graphs show the production levels of each phage over time; A: LESφ2; B: LESφ3; C: LESφ4. ■ + norfloxacin; □ – norfloxacin. D: Quantities of free phage were calculated by deducting prophage numbers from total phage numbers. The average free phage numbers at each time interval were plotted and Standard error is shown. Three independent experimental repeats were performed, each with 3 technical repeats.