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Flexibility of bacterial type IV pili determined using atomic force microscopy

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dc.contributor.advisor Dutcher, John R. Mogyoros, Joshua 2016-12-21T14:36:33Z 2016-12-21T14:36:33Z 2016 2016-12-06 2016-12-21
dc.description.abstract Type IV pili (T4P) are very thin protein filaments extended and retracted from the surface of certain Gram-negative bacteria. T4P play a major role in processes such as adhesion, twitching motility and biofilm formation. We improve on previous atomic force microscopy (AFM) measurements of the mechanical properties of T4P of Pseudomonas aeruginosa. A protocol was adapted and developed to perform single cell force spectroscopy (SCFS) by adhering a single bacterium to the end of a colloidal cantilever which is brought into contact with a substrate, allowing the pili to adhere. Force-distance curves are then collected by retracting the cantilever, corresponding to the stretching of the T4P. The persistence length, a parameter that characterizes the flexibility of a polymer, can be determined from the worm-like chain (WLC) model. The value of the persistence length measured by total internal reflection fluorescence (TIRF) microscopy is a factor of 1000 times greater than that measured in SCFS experiments. We show that the SCFS protocol is unlikely to be successful without rolling the bacteria beneath the cantilever, which could result in the T4P contacting the adhesive that coats the cantilever. We suggest that the persistence length discrepancy in the literature is due to a force-induced conformational change that occurs when pulling the T4P in the SCFS experiments. en_US
dc.language.iso en en_US
dc.subject type IV pili en_US
dc.subject Pseudomonas aeruginosa en_US
dc.subject atomic force microscopy en_US
dc.subject force spectroscopy en_US
dc.subject polymer physics en_US
dc.subject biophysics en_US
dc.subject persistence length en_US
dc.subject bacteria en_US
dc.subject physics en_US
dc.subject biology en_US
dc.subject biological physics en_US
dc.subject bacteria en_US
dc.subject pili en_US
dc.subject pilus en_US
dc.subject flexibility en_US
dc.subject T4P en_US
dc.subject single cell force spectroscopy en_US
dc.subject AFM en_US
dc.subject SCFS en_US
dc.subject P. aeruginosa en_US
dc.subject TIRF en_US
dc.subject total internal reflection fluorescence en_US
dc.subject worm-like chain model en_US
dc.subject WLC en_US
dc.title Flexibility of bacterial type IV pili determined using atomic force microscopy en_US
dc.type Thesis en_US Physics en_US Master of Science en_US Department of Physics en_US
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