Figure 6

DNase I and Proteinase K inhibit nicotine-induced biofilm formation. The biofilm formation of S. aureus USA300 strain was detected using a microtiter plate assay by measuring crystal violet stained biofilm at OD570. DNase I (25 U/well) and Proteinase K (2 ug/ml) was added to the well in both 2 mg/ml nicotine treatment group and control group. (A) Treated by DNaseI, the average thickness of biofilms varied from 1.506 ± 0.04 to 0.450 ± 0.07 in the nicotine-treated group (n = 3) and from 0.720 ± 0.14 to 0.328 ± 0.05 in untreated group. (n = 3) (B) Proteinase K(2 ug/ml) disrupted biofilm formation, in the nicotine treated group decreasing from 1.300 ± 0.06 to 0.393 ± 0.02 (n = 3), and in the control group decreasing from 0.721 ± 0.14 to 0.316 ± 0.08 (n = 3). *P < 0.05.