Regulation of Envelope Stress Responses in Escherichia coli

Abstract

The envelope of Gram-negative bacteria is a tightly regulated, intricate system, and as an essential component of these species, it is often the target of antibacterial treatments. Bacteria monitor and protect their envelope through a multitude of distinct stress response pathways, each with its own specialized role in maintaining a functioning envelope. Although these response pathways are each specialized for a particular type of stress, they are co-regulated and act as a network of stress responses rather than isolated pathways. Studying these pathways, both individually and as a network, provides insight into bacterial survival and may aid the design of antimicrobials. In this work, envelope stress response pathways of Escherichia coli are explored to elucidate the activation mechanisms driving individual pathways and to describe the co-regulatory properties linking the pathways. The production of outer membrane vesicles is examined for an entire knock-out library using a new, high-throughput dot-blot method. Based on these data, novel biological pathways are implicated in the production of vesicles and the link between vesiculation and the SigmaE stress response pathway is investigated. Further experiments on the SigmaE pathway lead to the discovery of a second necessary activation signal. Finally, the CPX stress response pathway is categorized as a general envelope stress response that is suppressed by the SigmaE pathway, creating a potentially exploitable weakness in the bacteria's defense.