FIG. 1.

Degradation of soluble ECM components by plasmin-coated B. burgdorferi. The substrates tested were human fibronectin (A), laminin (B), vitronectin (C), collagen type I (D), collagen type III (E), and collagen type IV (F). Spirochetes were incubated in HBSS with no additions (B-UT) and with addition of uPA alone (B-uPA), PLG alone (B-PLG), and PLG and uPA together to form spirochete surface-associated plasmin (B-Plasmin). A sham preparation to control for free plasmin carryover in the latter group consisted of PLG and uPA in HBSS but no B. burgdorferi. ELISA plate wells (six replicates) coated with substrate were incubated for 6 h with 10⁸ spirochetes from each experimental group. Undegraded substrate was detected, and percent degradation (a reduction in absorbance value was interpreted as substrate degradation) was calculated as described in Materials and Methods. Bars represent mean percent substrate degradation relative to the positive control (0% degradation) ± the standard deviation of six replicate wells for each experimental group. ∗, statistically significant (P < 0.0001); ∗∗, statistically significant (P < 0.01) compared to the positive control. The experiment was performed three times with similar results.