FIG 1.

OprF is a potential C3 binding acceptor on the P. aeruginosa surface. (A) Mid-log-phase P. aeruginosa was incubated with proteinase K (PK) at 37°C, washed with PBS, and incubated with 20% normal human serum. C3 binding to the bacterial surface was analyzed by flow cytometry. PK-treated bacteria showed reduced ability to bind to human complement C3b compared to untreated bacteria. (**, P ≤ 0.005, unpaired Student's t test). (B) Far-Western analysis showing C3b binding to P. aeruginosa OprF. P. aeruginosa membrane preparations were separated by SDS gel, transferred to nitrocellulose, renatured, and incubated with buffer (i) or normal human serum as a source of C3 (ii). Both blots were then washed and probed with anti-C3b antibody. ⭑, binding of C3 to OprF in the serum-treated blot at a molecular mass of ∼37 kDa.