Figure 7.

Structural investigation of the bacteria-HeLa cell interaction. (A) At low magnification the bacteria–HeLa cell contacts after cultivation on a grid are similar to the contacts observed by light microscopy (see Fig. 6). (B–D) Higher magnification reveals that the bacteria form needles during incubation at 37°C that pierce the HeLa cell membrane (arrows). This piercing and the secretion of Yops lead to a rapid rounding up of the HeLa cell. B, bacterium; H, HeLa cell; N, cell nucleus. (The scale bar in A is 1 μm and all other bars are 50 nm.)