Figure 3.

Assessment of K1 capsule and OmpA production, and the binding of C4bp and FH to LP OmpA⁺Escherichia coli. (a) Both OmpA⁺ and OmpA^–E. coli grown to LP and PEP were used for estimation of K1 capsule as described in the Materials and methods section. Data represent at least three separate experiments and are expressed as μg of K1 capsule ± SD per 10⁷ CFU. (b) Equal numbers of bacteria were suspended in SDS sample buffer containing β-mercaptoethanol and subjected to electrophoresis followed by Western blotting with an anti-OmpA antibody. Purified OmpA was included as a positive control. (c) and (d) Both LP and PEP OmpA⁺E. coli were incubated with 40% NHS for varying periods, the bacteria were collected by centrifugation, washed, dissolved in SDS buffer, and subjected to PAGE. After transferring the proteins to nitrocellulose, the blots were developed with anti-C4bp antibody (c) and anti-FH antibody (d). Purified C4bp and FH were loaded as positive controls on the gel.