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dc.contributor.authorConstantino, Maira Alves
dc.date.accessioned2018-03-06T18:30:10Z
dc.date.available2018-03-06T18:30:10Z
dc.date.issued2017
dc.identifier.urihttps://hdl.handle.net/2144/27383
dc.description.abstractThis work explores the effects of body shape and configuration of flagella on motility of Helicobacter pylori, a helical-shaped bacterium that inhabits the viscoelastic gastric mucosa and causes gastritis, ulcers and gastric cancer. Although it is well known that different shapes produce different hydrodynamic drag thus altering the speed and that helical shapes generate additional thrust this has not been quantitatively established for flagellated bacteria. Using fast time-resolution and high-magnification two-dimensional phase-contrast microscopy to simultaneously image and track individual H. pylori and its rod-shaped isogenic mutant in broth and mucin solutions, the shape as well as rotational and translational speed was determined. In collaboration with Professor Henry Fu and Mehdi Jabbarzadeh the experimental data was used to validate the method of regularized Stokeslets by directly comparing the observed speeds to numerical calculations. The results show that due to relatively slow body rotation rates, the helical shape makes at most a 15% contribution to speeds. In order to explore the effects of arrangement of flagella on motility three different Helicobacter spp. were examined: H. suis (bipolar, multiple flagella), H. cetorum (bipolar, single flagellum) and H. pylori (unipolar, multiple flagella) swimming in broth and mucin. Results show that regardless of media, the flagella bundles of bipolar bacteria can assume one of two configurations interchangeably: extended away from the body or wrapped around it. H. suis predominantly swims with the lagging flagella extended behind the body and the leading flagella wrapped around it, but cases where both bundles are extended or both are wrapped have also been observed. In addition the effects of varying pH on motility of H. suis in broth and mucin were investigated. In broth the rotational speed is not significantly affected by varying pH and the peak of the speed distribution shifts to lower values as the pH decreases. However in mucin the rotational speed decreases by a factor of 20 from pH5 to 4 and the motion is completely hindered below pH4. This indicates that H. suis is unable to move below pH4, in agreement with previous findings on H. pylori, due to gelation of mucin below pH4.en_US
dc.language.isoen_USen_US
dc.rightsAttribution-ShareAlike 4.0 International
dc.rights.urihttps://creativecommons.org/licenses/by-sa/4.0/
dc.subjectPhysicsen_US
dc.subjectBacteria motilityen_US
dc.subjectBacteria shapeen_US
dc.subjectBipolar flagellated bacteriaen_US
dc.subjectHelicobacter pylorien_US
dc.subjectMucinen_US
dc.subjectSwimming of flagellated microorganismsen_US
dc.titleInvestigating effects of morphology and flagella dynamics on swimming kinematics of different helicobacter species using single-cell imagingen_US
dc.typeThesis/Dissertationen_US
dc.date.updated2018-02-14T20:24:50Z
etd.degree.nameDoctor of Philosophyen_US
etd.degree.leveldoctoralen_US
etd.degree.disciplinePhysicsen_US
etd.degree.grantorBoston Universityen_US


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Attribution-ShareAlike 4.0 International
Except where otherwise noted, this item's license is described as Attribution-ShareAlike 4.0 International