Date of Award

December 2021

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Biological Sciences

First Advisor

Ching-Hong Yang

Committee Members

Mark McBride, Sonia Bardy, Sergei Kuchin, Douglas Steeber

Keywords

c-di-GMP, Dickeya dadantii, phytopathogen, two-component system, type III secretion system

Abstract

Bacteria respond to environmental cues through a variety of mechanisms. Two-component systems (TCSs) are a conserved mechanism used by bacteria to accurately respond and sense environmental changes. The monitoring of envelope perturbance is linked to TCS CpxA/CpxR in animal-infecting pathogens. The study of the TCS response regulator (RR) CpxR is largely unexplored in phytopathogens. This work focuses on the genetic linkage between cpxR and T3SS expression regulation. We identified the multiple roles of CpxR on several T3SS regulators and its participation in the bacterial second messenger (c-di-GMP) signaling cascade. Moreover, a compound library screening revealed a novel Cpx inducer CHIR-090, an inhibitor of lipid A biosynthesis. Although the linkage between Cpx response and lipid A biosynthesis remains unknown, we propose a potential role of CpxQ (a 3′-UTR sRNA from CpxR regulon gene cpxP mRNA) for relieving cells from the stress caused by lipopolysaccharide perturbance.

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