FIG 7.

Flow cytometry analysis of complement sensitivity of the hyperencapsulated ΔadcAII strain after transformation with locked SpnD39III (ST5556II) alleles (A to F) containing an inactivated creX gene. ΔFP441, ΔFP442, ΔFP443, ΔFP444, ΔMRO559, and ΔMRO560 are all double mutant strains carrying the adcAII mutation and an extra one in allele SpnIIIB, allele SpnIIIC, allele SpnIIIA, allele SpnIIID, allele SpnIIIE, and allele SpnIIIF, respectively. (A) Fluorescence index (MFI measured in arbitrary units multiplied by proportion of bacteria positive for C3b/iC3b) of C3b/iC3b deposition on ΔadcAII mutants and ΔadcAII fixed SpnD39III allele transformants (alleles A to F) as a proportion of the fluorescence index for the wild-type normal-capsule-thickness D39 strain. The data were measured using flow cytometry after preincubation in 30% human serum. Error bars represent SDs, and 10 transformants were tested for each double mutant strain. For all mutant strains, the P value for results compared to D39 was <0.001 (unpaired t tests). (B) Examples of flow cytometry histograms for C3b/iC3b deposition on WT D39 (dark gray line) and one ΔadcAII/SpnD39IIID allele (light gray line) double mutant transformant. Gray shading indicates the results for bacteria incubated in PBS alone.