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Life Sciences

Georgia State University

Theses/Dissertations

2006

Microbial ecology

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The Role Of Ecological Interactions In Polymicrobial Biofilms And Their Contribution To Multiple Antibiotic Resistance, Heather Adele O'Connell Dec 2006

The Role Of Ecological Interactions In Polymicrobial Biofilms And Their Contribution To Multiple Antibiotic Resistance, Heather Adele O'Connell

Biology Dissertations

The primary objectives of this research were to demonstrate that: 1.) antibiotic resistant bacteria can promote the survival of antibiotic sensitive organisms when grown simultaneously as biofilms in antibiotics, 2.) community-level multiple antibiotic resistance of polymicrobial consortia can lead to biofilm formation despite the presence of multiple antibiotics, and 3.) biofilms may benefit plasmid retention and heterologous protein production in the absence of selective pressure. Quantitative analyses of confocal data showed that ampicillin resistant organisms supported populations of ampicillin sensitive organisms in steady state ampicillin concentrations 13 times greater than that which would inhibit sensitive cells inoculated alone. The rate …


The Role Of Autoinducer-2 In Escherichia Coli Biofilm Formation And The Discovery Of A Plant-Derived Quorum Sensing Inhibitor, Chen Niu May 2006

The Role Of Autoinducer-2 In Escherichia Coli Biofilm Formation And The Discovery Of A Plant-Derived Quorum Sensing Inhibitor, Chen Niu

Biology Dissertations

The objectives of this work are: 1) to determine whether plant essential oil components influence the ability of Escherichia coli and several Pseudomonas species to form biofilms, and inhibit bacterial quorum sensing; 2) to understand the role of autoinducer-2 (AI-2) in biofilm formation by E. coli W3110. The biofilm formation assays determined that cinnamon, cassia and citronella oils differentially affected growth-normalized biofilm formation by E. coli. Cinnamaldehyde (CA) also inhibited the swimming motility of E. coli. Subinhibitory concentrations of CA were effective at inhibiting two types of acyl homoserine lactone (HSL) mediated quorum sensing (QS), and also AI-2 mediated QS. …