The effects of toxin-antitoxin system yefM-yoeB on Escherichia coli

Toxin-antitoxin (TA) systems are small genetic units abundant in bacterial genomes implicated in plasmid preservation and stress management. The yefM-yoeB family of TA systems is located on the chromosome and even some plasmids within several bacteria, including Escherichia coli. E. coli strains capable of causing disease outside the gastrointestinal tract belong to a diverse group of isolates referred to as extraintestinal pathogenic E. coli (ExPEC). ExPEC are the primary causative agents of urinary tract infections (UTIs) in humans. These strains are collectively known as uropathogenic Escherichia coli (UPEC), evolved a multitude of virulence factors and strategies to cause UTIs. The UPEC isolate CFT073 is the main pathogen that we are using to study TA systems. We also use a E. coli strain – MG1655 – to compare differences in TA systems between pathogenic and non-pathogenic strains of E. coli. To help understand these differences, we have cloned the yefM and yoeB loci of MG1655 and CFT073, creating plasmids containing inducible antitoxin or toxin. Additionally, we use yefM-yoeB knockout strains and test them under varying stresses. The yefM-yoeB knockout in CFT073 has already been shown to be defective in colonizing the murine urinary tract compared to WT CFT073. We are currently trying to identify and characterize the effects of these two genes on the bacterial host, including how these genes might affect resistance to different types of stresses. These differences will be elucidated by monitoring the mutant and WT strains growth in different medias as well as through in vitro competition experiments.