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There is now a CONTENT FREEZE for Mercury while we switch to a new platform. It began on Friday, March 10 at 6pm and will end on Wednesday, March 15 at noon. No new content can be created during this time, but all material in the system as of the beginning of the freeze will be migrated to the new platform, including users and groups. Functionally the new site is identical to the old one. webteam@gatech.edu
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In partial fulfillment of the Requirements for the Degree of
Doctor of Philosophy
in the
School of Biology
Samit Watve
Will defend his thesis
"Genetics of natural transformation and type six secretion in Vibrio cholerae"
Wednesday, November 16th, 2016
1:00 PM
Pettit Microelectronics Building , Rm 102 A&B
Thesis Advisor
Dr. Brian Hammer
School of Biological Sciences
Georgia Institute of Technology
Committee Members
Dr. Thomas DiChristina
School of Biological Sciences
Georgia Institute of Technology
Dr. Frank Stewart
School of Biological Sciences
Georgia Institute of Technology
Dr. Roger Wartell
School of Biological Sciences
Georgia Institute of Technology
Dr. Kostas Konstantinidis
School of Civil and Environmental Engineering
Georgia Institute of Technology
ABSTRACT
The facultative waterborne pathogen Vibrio cholerae transitions between its human host and the environment where it colonizes chitinous surfaces in aquatic settings. Growth on chitin coordinates the induction of sets of genes for 1) chitin utilization; 2) a type VI secretion system that allows contact-dependent killing of neighboring bacteria; and 3) DNA uptake by natural transformation, which is a mechanism for horizontal gene transfer. This thesis describes the regulatory network controlling these behaviors in V. cholerae and the consequences of their coordinate regulation. Results from high-throughput RNA sequencing (RNA-seq) show that transcription factor CytR is one of four positive regulators comprising the chitin-induced regulatory network. A combination of genetic and phenotypic assays reveal the four regulators control each behavior in a distinct manner in a commonly used clinical reference strain of V. cholerae. Whole genome sequencing and bioinformatics analyses of a set of strains isolated from diverse sources reveal novel type VI secretion system components present in environmental, but not clinical isolates. Finally, I show that chitin-induced natural transformation can facilitate horizontal gene transfer of distinct type VI secretion system genes between strains that have functional consequences. This thesis sheds light on diverse behavioral adaptations that allow this important human pathogen to spread and persist in the environment.
