Quantification of eDNA in SE1457 ΔsaeRS , SE1457, and SE1457 saec biofilms. eDNA was extracted from the unwashed 24 h biofilms of SE1457ΔsaeRS (white bars), SE1457 (black bars), and SE1457saec (gray bars). The eDNA in each biofilm was quantified by qPCR using primers specific for gyrA, serp0306, lysA, and leuA [19, 28]. The quantity of eDNA was calculated as follows: total eDNA (ng)/relative OD600. Results represent the mean ± SD of three independent experiments. WT, SE1457; SAE, SE1457ΔsaeRS; SAEC, SE1457saec.