Effect of DNaseI on SE1457 ΔsaeRS , SE1457, and SE1457 saec biofilm formation. SE1457ΔsaeRS, SE1457, and SE1457saec biofilms were washed and then stained with crystal violet. Their retained biomass was quantified by measuring the absorbance of each well at 570 nm. Biofilms were formed in the absence (black bars) or presence of DNase I (28 U/200 μL/well) (white bars). Mean values and standard deviations from three independent experiments are shown. (*), P < 0.05. WT, SE1457; SAE, SE1457ΔsaeRS; SAEC, SE1457saec.