A. James Clark School of Engineering
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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item A MATHEMATICAL MODEL TO STUDY THE ROLE OF THE LSR INTERGENIC REGION IN MEDIATION OF AUTOINDUCER-2 QUORUM SENSING IN ESCHERICHIA COLI(2013) Graff, Steven Meyer; Bentley, William E.; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Quorum sensing (QS) is a process that allows bacteria to communicate with each other to coordinate collective behavior in response to changes in environmental conditions. Their ability to mediate biofilm formation of biofilms and antibiotic resistance has created challenges on healthcare systems, and an impetus for us to understand QS systems. QS mediated by autoinducer-2 is likely to be the most common of these mechanisms. Recent work has elaborated on the LuxS-regulated (Lsr) system which can mediate and process AI-2 to QS-dependent behaviors, particularly regulatory elements including the lsr intergenic region and the repressor LsrR, the so-called QS"switch". In this thesis, we present a simulation of an example lsr-QS-system to elucidate the role of the lsr intergenic region binding site interactions and how this model integrates with recent literature on LsrR's protein structure to provide further details on the mechanisms of how the switch may operate in real systems.Item New Sensing Modalities for Bacterial and Environmental Phenomena(2013) Betz, Jordan; Rubloff, Gary W; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Intercellular communication is a ubiquitous phenomenon across all domains of life, ranging from archaea to bacteria to eukarya. In bacteria, this is often achieved using small molecules that allow bacteria to sense and respond to environmental cues about the presence, identity, and number of neighboring bacteria. This confers survival and competitive advantages to bacteria by providing a coordinated, population-scale response to a given stimulus in the environment. This dissertation describes the development of a microfluidic system for immobilizing and culturing of cells that also enables control over the genetic composition of the bacteria and their subsequent response to environmental stimuli via a new nonviral nucleic acid delivery mechanism. This nonviral nucleic acid delivery occurs outside the parameter space of traditional nonviral nucleic acid delivery methods such as electroporation and chemical transformation. The bacteria are immobilized in an optically clear alginate hydrogel which simulates the physical and chemical environment normally experienced by bacteria in a biofilm. Complementing the microfluidic cell culture work, surface enhanced Raman spectroscopy (SERS), a label-free vibrational spectroscopic technique that lends itself well to use in aqueous systems, was used to detect bacterial signaling molecules. SERS was performed with three different examples of bacterial communication molecules: the universal quorum sensing molecule autoinducer-2 (AI-2), the species-specific Pseudomonas Quinolone Signal (PQS), and the stationary phase indicator molecule indole. SERS substrates were formed by galvanic displacement, a substrate fabrication method that can be adapted to many SERS applications. Taken together, these new sensing modalities represent a step toward developing systems that allow researchers to investigate, understand, and ultimately control a cell's response to its environment.Item Inhibitors of Autoinducer-2 Quorum Sensing and Their Effect on Bacterial Biofilm Formation(2007-07-31) Lennen, Rebecca Melissa; Bentley, William E; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Bacteria utilize small signaling molecules, or autoinducers, to regulate their gene expression in tandem by a process termed quorum sensing. The gene encoding the synthase for autoinducer-2 (AI-2), luxS, is conserved in dozens of diverse bacteria. Behaviors controlled by AI-2 include virulence, motility, toxin production, and biofilm formation. The development of therapies that interfere with AI-2 quorum sensing are attractive for targeting biofilms, which exhibit inherent resistance to most antibiotics and biocidal agents. In this study, in vitro synthesized AI-2, LuxS inhibitors, and (5Z)-4-bromo-5-(bromomethylene)-3-butyl-2(5H)-furanone were screened for their effect on biofilm formation in Escherichia coli, Bacillus cereus, and Listeria innocua. The LuxS inhibitors were found to have no influence on biofilm formation in any of the screened species, but reduced exponential phase AI-2 production in Listeria innocua. The brominated furanone significantly inhibited growth in B. cereus and L. innocua, and under certain conditions preferentially inhibited biofilm formation independently from growth.