SDS-PAGE analysis of anti-BamA co-IP elutions. Cultures of B. burgdorferi strain B31 MI (2 × 1010 organisms per sample) were washed and solubilized, and the protein-containing cell lysate was used for co-immunoprecipitation (co-IP) experiments using anti-Thio and anti-BamA polyclonal antibodies. Lanes 1-4 of the Coomassie-stained SDS-PAGE gel shows the 40 kDa region from elutions of anti-BamA co-IP experiments using increasing amounts (5 μL, 10 μL, 20 μL, or 40 μL) of antibody (titration indicated by grey triangle). An unknown protein that was enriched with increasing amount of anti-BamA antibody is indicated at left (arrow). A sample from the anti-Thio elutions (from which 40 μL antibody was used for co-IP) is shown in lane 5.