S. epidermidis agr system controls extracellular DNA release through atlE . (a) Biofilm-associated gene transcripts were compared between 1457 wt, △ agr and △ agr/atlE by using qRT-PCR. (b) Extracellular DNA release from cultures in microtitre plates was quantified as described above. Error bars represent the S.E.M. for three independent experiments. (c-h) S. epidermidis 1457 wild type (wt, c-d) agr mutant (△ agr, e and f) and agr/atlE double mutant (△ agr/atlE, g and h) were grown for 24 h in flow chambers irrigated with minimal medium, and were then stained with DDAO for extracellular DNA in biofilms, upon which microscopic investigation was performed by CLSM. The 3-D images ( d/ f/ h) were generated using the IMARIS, bars, 50 μm.