BamA is required for efficient BB0324-BB0028 interactions. Protein lysate from B. burgdorferi strain flacp-795-LK cultures (grown in 0.05 and 1.0 mM IPTG) and the parental strain B31-A3-LK cultures (grown in IPTG-deplete media) was used for co-IP using anti-Thio, anti-BB0324, and anti-BB0028 polyclonal antibodies (indicated above panels). Equal amounts of each co-IP elution were subjected to SDS-PAGE and immunoblot analysis. A. Anti-BB0324 immunoblots of the various co-IP elutions from the parental B31-A3-LK cultures (LK; top panel), flacp-795-LK cultures cultivated in 1.0 mM IPTG (middle panel), and flacp-795-LK cultures cultivated in 0.05 mM IPTG (bottom panel). B. Co-IP elutions were immunoblotted as in A, except with anti-BB0028 antisera. C. BamA depletion does not affect total cellular levels of BB0324 or BB0028. Prior to the cell lysis and solubilization procedure, spirochetes from each culture condition were washed and prepared as whole-cell lysates (WCL). Equal amounts of WCL (generated from 4 × 107 organisms) were subjected to anti-BamA immunoblot analysis in order to confirm the flacp-795-LK regulatable phenotype. The WCL were also immunoblotted with BB0324, BB0028, and Lp6.6 antisera to determine if cellular levels of each protein were affected by BamA depletion. A FlaB immunoblot is included to ensure equal loading of the B. burgdorferi WCL samples.