The Mar, Sox, and Rob Systems.

Environments inhabited by are diverse and often stressful. This is particularly true for and during host association in the gastrointestinal systems of animals. There, and must survive exposure to various antimicrobial compounds produced or ingested by their host. A myriad of changes to cellular physiology and metabolism are required to achieve this feat. A central regulatory network responsible for sensing and responding to intracellular chemical stressors like antibiotics are the Mar, Sox, and Rob systems found throughout the . Each of these distinct regulatory networks controls expression of an overlapping set of downstream genes whose collective effects result in increased resistance to a wide array of antimicrobial compounds. This collection of genes is known as the regulon. This review will provide an overview of the regulon and molecular architecture of the Mar, Sox, and Rob systems.