FIG. 3.

Degradation of radiolabeled, insoluble R22 ECM by plasmin-coated B. burgdorferi. ECM components were labeled preferentially with [³⁵S]methionine-cysteine (noncollagenous protein) (A), [³H]fucose (glycoprotein) (B), and [³H]proline (collagen) (C). 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. ECMs were incubated for 6 h with 10⁸ spirochetes from each experimental group. Released (supernatant) and unreleased (2 N NaOH digest of undegraded ECM) radioactivity was counted for each well. Percent release of the total radioactive counts present in each well was calculated as described in Materials and Methods. Bars represent mean percent radioactivity release ± standard deviation of five replicate wells per experimental group. ∗, statistically significant (P < 0.01) compared to HBSS control. The experiment was performed twice with similar results.