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Shaun W. Lee,1,
Aurelie Snyder,2
Nathan J. Weyand,1,
Antony Bakke,3 and
Magdalene So1*
Department of Molecular Microbiology and Immunology,1 Microscopy Core Facility,2 Department of Pathology, Oregon Health and Science University, 3181 SW Sam Jackson Park Rd., Portland, Oregon 972393
Received 18 May 2007/ Returned for modification 16 July 2007/ Accepted 24 July 2007
Neisseria gonorrhoeae is the bacterium that causes gonorrhea, a major sexually transmitted disease and a significant cofactor for human immunodeficiency virus transmission. The retactile N. gonorrhoeae type IV pilus (Tfp) mediates twitching motility and attachment. Using live-cell microscopy, we reveal for the first time the dynamics of twitching motility by N. gonorrhoeae in its natural environment, human epithelial cells. Bacteria aggregate into microcolonies on the cell surface and induce a massive remodeling of the microvillus architecture. Surprisingly, the microcolonies are motile, and they fuse to form progressively larger structures that undergo rapid reorganization, suggesting that bacteria communicate with each other during infection. As reported, actin plaques form beneath microcolonies. Here, we show that cortical plaques comigrate with motile microcolonies. These activities are dependent on pilT, the Tfp retraction locus. Cultures infected with a pilT mutant have significantly higher numbers of apoptotic cells than cultures infected with the wild-type strain. Inducing pilT expression with isopropyl-ß-D-thiogalactopyranoside partially rescues cells from infection-induced apoptosis, demonstrating that Tfp retraction is intrinsically cytoprotective for the host. Tfp-mediated attachment is therefore a continuum of microcolony motility and force stimulation of host cell signaling, leading to a cytoprotective effect.
Published ahead of print on 6 August 2007.
Supplemental material for this article may be found at http://iai.asm.org/.
Present address: Department of Immunobiology and BIO5 Institute, University of Arizona, Tucson, AZ 85718.
Present address: Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093-0721.
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