Figure 2.

Disruption of wcjE in a serotype 9V strain of Streptococcus pneumoniae resulting in the 9A phenotype. A, The serotype 9V parent strain JC01 has an intact wcjE gene, which was disrupted by recombination deletion with a Janus cassette to create the transformant JC02. Thick lines and circled numbers denote the polymerase chain reaction (PCR)–amplified regions depicted in panel B. Also shown are the lengths of the delineated areas of DNA (bp, base pairs). B, PCR products of the parent strain JC01 (1) and the transformant JC02 (2). C, Results of Quellung assays for JC01 (left) and JC02 (right) with factor sera 9d (top) and 9g (bottom). The triangles point to bacteria reacting positively in the assay (ie, displaying a halo). D, Flow cytometry histograms demonstrating factor sera 9d (top) and 9g (bottom) binding to JC01 (gray line) and JC02 (black line). The signal of the negative control bacteria (ie, treated with secondary antibody alone) is depicted by the peak with gray fill.