Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 98, Issue 12, Pages 6901-6904Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.121171698
Keywords
Pseudomonas aeruginosa; twitching motility; fluorescence
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Type IV pill are thin filaments that extend from the poles of a diverse group of bacteria, enabling them to move at speeds of a few tenths of a micrometer per second. They are required for twitching motility. e,g,, in Pseudomonas aeruginosa and Neisseria gonorrhoeae, and for social gliding motility in Myxococcos xanthus, Here we report direct observation of extension and retraction of type IV pill in P. aeruginosa, Cells without flagellar filaments were labeled with an amino-specific Cy3 fluorescent dye and were visualized on a quartz slide by total internal reflection microscopy. When pill were attached to a cell and their distal ends were free, they extended or retracted at rates of about 0.5 mum s(-1) (29 degreesC). They also flexed by Brownian motion, exhibiting a persistence length of about 5 mum. Frequently, the distal tip of a filament adsorbed to the substratum and the filament was pulled taut. From the absence of lateral deflections of such filaments, we estimate tensions of at least 10 pN. Occasionally, cell bodies came free and were pulled forward by pilus retraction. Thus, type IV pill are linear actuators that extend, attach at their distal tips, exert substantial force, and retract.
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