FIG 2.
c-di-AMP is released from S. aureus biofilms. c-di-AMP levels were quantified in extracellular fractions (biofilm-conditioned medium) and intracellular fractions from wild-type S. aureus (LAC) and isogenic ΔgdpP static biofilms by using UPLC-MS/MS. Viable bacteria were quantified, and c-di-AMP values were plotted per 109 CFU for normalization. The percentage of total c-di-AMP detected in biofilm-conditioned medium after 2 (A), 4 (B), and 6 (C) days of growth are indicated. Error bars represent standard deviations of the average results from at least two independent experiments, with individual data points plotted. Results were analyzed using Student's t test to compare wild-type LAC and ΔgdpP fractions. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001.