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Influence of Type IV Pilus Retraction on the Architecture of the N. gonorrhoeae-Infected Cell Cortex

¹ University of Arizona;
² Columbia University

Early in infection, Neisseria gonorrhoeae can be observed to attach to the epithelial cell surface as microcolonies and induce dramatic changes to the host cell cortex. We tested the hypothesis that Tfp retraction plays a role in the ultrastructure of both the host cell cortex and bacterial microcolony. Using serial ultra-thin sectioning, Transmission Electron Microscopy and 3D reconstruction of serial 2D images, we have obtained the first 3D reconstructions of the N. gonorrhoeae-host cell interface, and determined the architecture of infected cell microvilli as well as the attached microcolony. Tfp connect both wt and Tfp-retraction-deficient bacteria with each other, and with the host cell membrane. Tfp fibers and microvilli form a lattice in the wt microcolony and at its periphery. Wt microcolonies induce microvillus formation and surface area increases, leading to a ~9-fold increase in the surface area of the host cell membrane at the site of attachment. In contrast, Tfp-retraction-deficient microcolonies did not affect these parameters. Wt microcolonies had a symmetrical, dome-shaped structure with a circular "footprint" while Tfp-retraction-deficient microcolonies were notably less symmetrical. These findings support a major role for Tfp retraction in microvillus and microcolony architecture. They are consistent with the biophysical attributes of Tfp and the effects of Tfp retraction on epithelial cell signaling.

³ E-mail: higashid{at}email.arizona.edu