Characteristics of strains APEC94, APEC94Δlsr(Cm) and lsr-APEC94Δlsr. A Growth curves of APEC94, APEC94Δlsr(Cm) and lsr-APEC94Δlsr in LB. The growth rates of APEC94, APEC94Δlsr(Cm) and lsr-APEC94Δlsr were monitored by measuring their OD600 values in LB medium at 1-h intervals for 12 h, respectively. After 12 h of culturing, there was no significant difference in the growth rate of APEC94, APEC94Δlsr(Cm) and lsr-APEC94Δlsr grown in LB broth (p > 0.05). Each value represents the average of three independent experiments. Significant differences were detected using the Student’s t test with SPSS v19.0 software. B Biofilm formation. There was no significant difference in biofilm formation among APEC94, APEC94Δlsr(Cm) or lsr-APEC94Δlsr strains (p > 0.05). All assays were performed in triplicate and repeated three times. p-values of less than 0.05 were considered significant. C Bacterial motility. The swimming motility of strain APEC94Δlsr(Cm) was significantly lower than that of the wild-type APEC94 strain (p < 0.01) while the swimming motility of complementary strain lsr-APEC94Δlsr was restored. The experiment was repeated three times and all samples were measured in triplicate. p values less than 0.05 were considered significant.