FIG 3.
Effects of S. gordonii or A12 supernatants on PcomX or PcipB promoter activity. S. mutans containing lacZ fused to the promoter of comX (A) or cipB (B) was grown to an OD600 of 0.15 in FMC medium (A) or BHI medium (B). Supernatants from overnight cultures of the indicated strains were obtained after centrifugation, the pH was adjusted to 7.0 with 6 N NaOH, and the solutions were filter sterilized. In the case of FMC conditions, supplemental glucose was added to increase the concentration of glucose by 25 mM. Synthetic peptides (XIP or CSP) were added to the supernatants and incubated overnight (for XIP) or for 2 h (for CSP). The reporter strains were grown to an OD of 0.15, and cells were collected by centrifugation and then were resuspended in the indicated supernatants for 2 h prior to measuring β-galactosidase activity. All assays were performed at least three times, with technical triplicates. The bars are averages and error bars represent SDs. Asterisks indicate statistically significant differences between wild-type A12 (400 nM XIP) and A12 ΔpcfO (400 nM XIP) (A) and between wild-type A12 and A12 Δsgc or A12 ΔpcfO. (B). Statistical analysis was performed using an unpaired Student t test. *, P < 0.05. ns, not significant.