Figure 4

Repressing wcaF gene did not significantly affect biofilm tolerance against erythromycin. (a) The biofilm level of experimental group (gRNA induced at 6^th hour and cultured to 8^th hour) was similar to control group (gRNA−) grown to 6^th hour. After treating with erythromycin and followed by Live/Dead Baclight assay, some red fluorescence was observed, showing some cells were dead or their membranes were damaged. From the zoom in images, it can be observed that the control biofilm (gRNA−) grew to 6^th hour had relatively more red fluorescence as compared to the control biofilm (gRNA−) grew to 8^th hour. (b) The total biomass of experimental group (gRNA+) was similar to the one of control group (gRNA−) grown to 6^th hour, and they were lesser than the control group (gRNA−) grown to 8^th hour. (c) The live cells ratio of control group (gRNA−) grown to 6^th hour was significantly lesser than the control group (gRNA−) grown to 8^th, which shows biofilm tolerance to erythromycin increases during biofilm developing. The live cells ratio of experimental group (gRNA−) had no significant difference from both control groups (gRNA−) that grown to 6^th hour. Scale bars, 50 μm. All data are represented as mean ± std_dev (n = 3). *indicates P value < 0.05.