Fig 4.

Capsule analyses. (A) Bacterial adherence to A549 epithelial cells. A549 epithelial cells were infected at an MOI of 50:1 with the WT and the ΔarcD mutant of strains D39 and R6. Input and cell-associated (adherence) bacteria were enumerated by plating from serial dilutions. Data shown are the means of three independent experiments. Error bars denote SEMs. *, P < 0.05. (B) Capsule assay of the R6 WT, the D39 WT, and its derivatives using a quantitative determination of uronic acids. Data shown are the means of three independent experiments. Error bars denote SEMs. *, P < 0.05. (C) Capsule assay of ST556 and its ΔarcD mutant using Stains-All reagent. Note that the different wavelengths indicated in panels B and C are due to different experimental procedures as described in Materials and Methods. (D) Capsule staining using immunofluorescence. The D39 WT and its ΔarcD mutant were detected using antiserum against pneumococcal type 2 capsule polysaccharides (indicated with arrows). Data are representative of two independent experiments. (E) Detection of capsule by LRR staining and transmission electron microscopy. Capsules are indicated with asterisks. Note that the magnification bars for the D39 and ST556 strains are in different scales to show the entire capsules.