FIG 4.

pH drop assays. Cells of S. mutans UA159 were grown to mid-exponential phase in TV base medium supplemented with 20 mM glucose (glc), 20 mM glc and 20 mM GlcNAc (glc/GlcNAc), or 20 mM GlcNAc (GlcNAc) before being subjected to pH drop assays as described in Materials and Methods. The assay was initiated by the addition of 50 mM (final concentration) of either GlcNAc (A) or glucose (B), and the change in the pH was monitored at 30-s intervals for 30 min. The data represent the averages of results of three independent experiments, with error bars indicating the standard deviation.