Effects of bacterial cells without and with its cell-free culture filtrate
Bacterial cultures were centrifuged at 3000g for 5min at 4°C to pellet the cells. The supernatants were removed and the bacterial cells were washed with sterile water three times. Then the cells were resuspended in PDB dilutions (PDB 1:50) to yield different working concentrations (0.33, 1, 1.67, 2.33, 3.0 and 3.67 × 107CFUmL−1, using dilution plating on nutrient agar). These solutions were used to bioassay for trap formation. The negative controls were PDB dilutions (PDB 1:50). The experiments were prepared in triplicate and repeated three times.