FIG 4.

Deoxycholic acid kills pneumococci with a deficient autolytic mechanism. (A) S. pneumoniae strain R6 wt, or isogenic double mutant ΔlytAΔlytC or ΔspxBΔlctO were inoculated in six-well plates containing THY, and bacteria were incubated for 4 h. The supernatants were obtained and filter-sterilized, and the eDNA was purified. This eDNA was used as a template in species-specific quantitative PCRs (qPCRs) along with DNA standards for quantification purposes. *, P < 0.037 compared to R6 WT. (B) R6 WT or its isogenic ΔlytAΔlytC mutant was inoculated at a density of ∼5.15 × 10⁸ CFU/ml in THY broth and left untreated (control) or treated with 0.5 mg/ml of DoC. Bacteria were incubated for 2 h at 37°C in a 5% CO₂ atmosphere, after which the cultures were serially diluted and plated onto blood agar plates to obtain the density (CFU/ml). #, P = 0.33 compared to R6 WT strain treated with DoC. In panels A and B error bars represent the standard errors of the means calculated using data from at least three independent experiments.