Fig. 3.

Carolacton activity depends on pH. Carolacton was added to phosphate-buffered (75 and 100 mM) and unbuffered (unbuff.) THBS media before inoculation with S. mutans UA159 to an OD₆₀₀ of 0.01. Two different carolacton concentrations were tested, 0.25 μg/ml (crosshatched bars) and 2.5 μg/ml (gray bars). The media differed in buffer concentration (75 mM versus 100 mM) and in the initial pH (7.8 versus 6.5). After 20 h, biofilms were washed and stained with LIVE/DEAD viability staining. The inhibition of viability was calculated relative to untreated control wells (see Materials and Methods). Control wells contain the same amount of methanol as used for the carolacton-treated wells but lacked carolacton. Standard deviations were calculated from 3 independent biological replicates, each consisting of 5 technical replicates. The mean of the OD₆₀₀ is shown as a line graph.