Figure 1.

Collagen VI kills NTHi by membrane permeabilization and rupture. (A) Bacteria were incubated with 2 μM collagen VI for 0, 30, 60, and 120 min at 37°C, respectively. (B) Bacteria were treated with different molar quantities of LL-37 or collagen VI between 10 nM and 2 μM, as indicated, for 2 h at 37°C, respectively. Numbers of bacterial colonies after incubation with collagen VI were determined in viable count assays. Incubation in buffer alone (untreated) or LL-37 served as negative and positive controls, respectively. The dots represent individual experiments with the respective strains. Values are expressed as percent bacterial survival. (C–F), negative staining and transmission electron microscopy, (G–J) scanning electron microscopy of NTHi killing. Incubation with collagen VI leads to membrane blebbing (arrowheads) and exudation of cytoplasmic contents (arrows). Finally, large scale membrane destabilization severely impairs NTHi architecture (F, J). The scale bars represent 500 nm (C–F) and 1 μm (G–J).