Figure 2.

Nuclease activity is reduced during biofilm formation. (a) Fluorescence intensity of a FRET-based DNA probe assay in 20 h old planktonic cultures and biofilms of S. aureus Newman WT on glass, silanized glass and Pluronic F-127-coated silanized glass. Dots indicate the mean of 4 different planktonic cultures and 6 biofilms grown with three different bacterial cultures. Lines are least square fits of Eq. (1) to the measured intensity data. Error bars are eliminated for easy readability. (b) Nuclease concentration per CFU was determined in 20 h old planktonic cultures and biofilms of S. aureus Newman WT and S. aureus Newman ∆nuc1 grown on glass, silanized glass and Pluronic F-127-coated silanized glass. Bars indicate the mean of 4 different planktonic cultures and 6 biofilms grown with three different bacterial cultures. Error bars show the standard error of the mean. Statistical significance between WT and mutant strain on the same solid surfaces is indicated with asterisks, **P ≤ 0.01; ***P ≤ 0.001.