Mechanisms and regulation of horizontal gene transfer by natural transformation in Vibrio cholerae

点击翻译按钮获取中文摘要

Project Summary The Dalia lab studies the regulation and mechanisms of horizontal gene transfer by natural transformation (NT) using Vibrio cholerae as a model system. While this bacterium is the causative agent of the diarrheal disease cholera, we do not seek to study bacterial pathogenesis. Instead, we leverage this well- established model system and the genetic tools we have developed to characterize NT in a physiologically relevant context. NT contributes to the rapid spread of antibiotic resistance determinants and virulence factors in bacterial pathogens. Thus, characterizing the regulation and mechanisms of NT may uncover novel approaches to combat diverse clinically relevant infections. The genes required for NT are tightly regulated, and only induced when V. cholerae forms biofilms on the chitinous shells of crustacean zooplankton in the aquatic environment. The formation of chitin biofilms is also important for the survival of this facultative pathogen in its environmental reservoir, and promotes the waterborne transmission of cholera. Vibrio-chitin interactions can be easily studied in a lab setting, which provides a physiologically relevant and highly tractable model system for studying NT. In the next five years, we will focus on three major areas. First, V. cholerae uses dynamic surface appendages called type IV pili to bind to chitinous surfaces and to take up DNA for NT. The mechanisms that regulate the dynamic extension and retraction of these appendages, however, remains poorly characterized. Using tools we helped develop to label type IV pili in live cells, we will address how motor ATPases, minor pilins, and other environmental cues regulate pilus dynamic activity. Second, we will study how two membrane-embedded DNA-binding transcription factors, ChiS and TfoS, coordinate to activate the chitin regulon in V. cholerae. Membrane- embedded regulators are understudied, and this work will help elucidate the dynamics and constraints for the DNA-binding activity of membrane-embedded vs soluble transcription factors. Third, we will use a combination of cell biological and genetic approaches to study horizontal gene transfer by natural transformation. Namely, we will address the spatiotemporal dynamics of natural transformation within chitin biofilms; and the impact of neighbor predation on these dynamics. Also, we will formally test the long-standing, yet untested, hypothesis that DNA uptake during natural transformation plays an important nutritional role. Together, our basic research extends a fundamental understanding of a number of critical and conserved processes (e.g. pili, signal transduction, horizontal gene transfer) that are shared by diverse microbial species, including many pathogens.