The assay of biofilm formation was performed as previously reported with some modifications (Sun et al. 2017 (link)). In brief, 50 μL aliquots of each culture were inoculated into 5 mL fresh LB medium (with or without aTc) contained in two different 6-well polystyrene culture plates (final OD600 of ~ 0.05), followed by incubating at 37 °C without shaking for 24 h. Then, the medium was discarded, and the wells were gently rinsed with 1X PBS to remove planktonic and loosely adhered cells. The adhered biofilm was quantified by staining the cells with 1% crystal violet solution for 30 min at room temperature. The excess crystal violet was removed by washing the wells three times with distilled water. Crystal violet bound to the adhered cells was solubilized in 1 mL of 95% ethanol and quantified by measuring absorbance at 540 nm and 620 nm. For biofilm assay using a differential interference microscope (Olympus U-LH100-3, Japan), the sterilized coverslips were added to the well after inoculation as described above. After incubation for 24 h, the coverslips were taken out and washed gently using PBS buffer (0.15 M, pH 7.2) to remove the planktonic cells. The biofilm formation of each tested group was captured using the microscope. All experiments were performed with three independent biological replicates.