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Tactic behaviors in bacterial dynamics

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dc.contributor.advisor Roman Stocker. en_US Sekora, Michael David en_US
dc.contributor.other Massachusetts Institute of Technology. Dept. of Physics. en_US 2006-05-15T20:39:00Z 2006-05-15T20:39:00Z 2005 en_US 2005 en_US
dc.description Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2005. en_US
dc.description Includes bibliographical references (leaves 89-90). en_US
dc.description.abstract The locomotion of a wide class of motile bacteria can be mathematically described as a biased random walk in three-dimensional space. Fluid mechanics and probability theory are invoked to model the dynamics of bacteria swimming using tactic behaviors (movements or reorientation in response to chemical, physical or environmental stimuli) in flowing, viscous media. Physical descriptions are developed for bacterial chemotaxis (response to chemical agents) near particles exuding attractants, a small-scale process with global-scale implications for the biogeochemistry of the oceans. Three cases were investigated: a stationary particle, a slowly moving particle and a particle that generates a hydrodynamic wake in the form of attached vortices. The key finding of this thesis consists in the discovery of several scenarios in which motile bacteria swimming via random walks put themselves at a disadvantage in their quest for food with respect to non-motile pacteria. Thus, there exist threshold values in nutrient gradients and bacterial chemosensory ability below which bacteria would be better served if they did not swim. In the presence of vortices, it was discovered that bacteria can exploit the recirculating flow field to vastly increase their nutrient supply, but only if they alter their swimming behavior as a function of the concentration field. en_US
dc.description.abstract (cont.) Otherwise, slow bacteria completely miss the hydrodynamic wake (and the high nutrient region) behind a nearby moving particle, while fast bacteria end up colonizing the particle (i.e. clustering around the particle and potentially anchoring themselves to it). These processes are currently under investigation in laboratory experiments using high-speed digital photography, for which software (BacTrackTM) was written that can locate and track multiple bacteria over time, with the aim of providing trajectories and their statistics and ultimately establish the importance of these phenomena for marine ecology and biogeochemistry. Preliminary experiments were conducted with Escherichia coli being exposed to ultraviolet radiation, documenting the known result of E. coli being repelled by UV radiation and providing a successful test bed for the reliability of the tracking software. en_US
dc.description.statementofresponsibility by Michael David Sekora. en_US
dc.format.extent 127 leaves en_US
dc.format.extent 7153932 bytes
dc.format.extent 7160068 bytes
dc.format.mimetype application/pdf
dc.format.mimetype application/pdf
dc.language.iso eng en_US
dc.publisher Massachusetts Institute of Technology en_US
dc.rights M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. en_US
dc.subject Physics. en_US
dc.title Tactic behaviors in bacterial dynamics en_US
dc.type Thesis en_US S.B. en_US
dc.contributor.department Massachusetts Institute of Technology. Dept. of Physics. en_US
dc.identifier.oclc 62763478 en_US

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