{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,10]],"date-time":"2026-06-10T15:33:29Z","timestamp":1781105609657,"version":"3.54.1"},"reference-count":36,"publisher":"National Academy of Sciences","issue":"12","content-domain":{"domain":["www.pnas.org"],"crossmark-restriction":true},"short-container-title":["Proc. Natl. Acad. Sci. U.S.A."],"published-print":{"date-parts":[[2001,6,5]]},"abstract":"<jats:p>\n                    Type IV pili are thin filaments that extend from the poles of a\n diverse group of bacteria, enabling them to move at speeds of a few\n tenths of a micrometer per second. They are required for twitching\n motility, e.g., in\n                    <jats:italic>Pseudomonas aeruginosa<\/jats:italic>\n                    and\n                    <jats:italic>Neisseria gonorrhoeae<\/jats:italic>\n                    , and for social gliding motility\n in\n                    <jats:italic>Myxococcus xanthus<\/jats:italic>\n                    . Here we report direct observation\n of extension and retraction of type IV pili in\n                    <jats:italic>P.\n aeruginosa<\/jats:italic>\n                    . Cells without flagellar filaments were labeled with\n an amino-specific Cy3 fluorescent dye and were visualized on a quartz\n slide by total internal reflection microscopy. When pili were attached\n to a cell and their distal ends were free, they extended or retracted\n at rates of about 0.5 \u03bcm s\n                    <jats:sup>\u22121<\/jats:sup>\n                    (29\u00b0C). They also flexed\n by Brownian motion, exhibiting a persistence length of about 5 \u03bcm.\n Frequently, the distal tip of a filament adsorbed to the substratum and\n the filament was pulled taut. From the absence of lateral deflections\n of such filaments, we estimate tensions of at least 10 pN.\n Occasionally, cell bodies came free and were pulled forward by pilus\n retraction. Thus, type IV pili are linear actuators that extend, attach\n at their distal tips, exert substantial force, and retract.\n                  <\/jats:p>","DOI":"10.1073\/pnas.121171698","type":"journal-article","created":{"date-parts":[[2002,7,26]],"date-time":"2002-07-26T10:44:19Z","timestamp":1027680259000},"page":"6901-6904","update-policy":"https:\/\/doi.org\/10.1073\/pnas.cm10313","source":"Crossref","is-referenced-by-count":542,"title":["Direct observation of extension and retraction of type IV pili"],"prefix":"10.1073","volume":"98","author":[{"given":"Jeffrey M.","family":"Skerker","sequence":"first","affiliation":[{"name":"Rowland Institute for Science, Cambridge, MA 02142; and Department\r of Molecular and Cellular Biology, Harvard University, Cambridge, MA\r 02138"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Howard C.","family":"Berg","sequence":"additional","affiliation":[{"name":"Rowland Institute for Science, Cambridge, MA 02142; and Department\r of 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