whole cells that produce surface exposed BBA33 mediate specific binding to type VI collagen. B. burgdorferi strain ML23 pBBE22luc (P; parent), HZ001 pBBE22luc (M; Δbba33 mutant) and HZ001 pHZ300 (C; complement) were grown either under ‘noninducing’ conditions (32°C, 1% CO2, pH 7.6; left side) or ‘inducing’ conditions (37°C, 5% CO2, pH 6.8; right side) and incubated on cover slips containing either laminin (filled circles or squares) or type VI collagen (open circles or squares). B. burgdorferi cells binding was scored via dark field microscopy. Each data point represents the average number of spirochetes visualized in 10 random fields. Each strain was tested a minimum of three times, with each sample assayed in duplicate. ***P < 0.001; ****P < 0.0001; ns, nonsignificant difference.