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Author ORCID Identifier


Open Access Dissertation

Document Type


Degree Name

Doctor of Philosophy (PhD)

Degree Program

Molecular and Cellular Biology

Year Degree Awarded


Month Degree Awarded


First Advisor

Kevin Griffith

Second Advisor

John Lopes

Third Advisor

Elizabeth Vierling

Fourth Advisor

Peter Chien

Subject Categories



Living organisms generally share a small number of characteristics, among which include maintaining homeostasis, growth, and responding to changing environments. Wherever we find life, we typically observe this life performing these tasks. Likely no environment is truly barren, so organisms must be able to continue living in crowded conditions. Humans use their senses to determine the quality of their local environment. Individuals use languages, written, spoken and digital to communicate these findings to their neighbors. Bacteria have evolved complex systems to sense these conditions, and to trigger appropriate developmental programs to help them survive, grow, and respond in changing environments. Bacteria both produce and sense signals about these density-dependent conditions in a process called quorum sensing. Chapter 1 provides an introduction to the mechanisms utilized by bacteria referred to as quorum sensing. An overview is given of the history of the study of these mechanisms, as well as a review of molecules and strategies from both Gram-negative and Gram-positive organisms. Also discussed here are mechanisms of quorum quenching used by organisms in quorum sensing pathways. Next, we discuss in some detail the molecular mechanisms used by Bacillus subtilis to regulate pathways under control of the quorum response. Chapter 2 describes work looking to further explain the mechanism of ComA activation. In this chapter, we use a genetic screen to identify constitutive mutants of ComA. We then characterize these mutants for their regulation by ComP and RapC and for their ability to bind DNA. These results were used in an attempt to generate a computational model of ComA activation. We take preliminary steps in validating this model by logically creating and testing combination mutants of ComA. The role of acetyl-phosphate in ComA activation is also briefly explored. Chapter 3 explores the role of Rap proteins in regulating the biological processes of genetic competence, sporulation, motility and biofilm formation. We were able to characterize several Rap proteins as novel regulators of these pathways. We also were able to show that Rap60 uses a separate surface for interaction with ComA as compared to canonical Rap protein anti-activators of genetic competence.


Creative Commons License

Creative Commons Attribution-Noncommercial 4.0 License
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