Molecular Profiling: Catecholamine Modulation of Gene Expression in Escherichia coli O157:H7 and Salmonella enterica Serovar Typhimurium

Investigations of Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium have demonstrated that these bacterial pathogens can respond to the presence of catecholamines including norepinephrine and/or epinephrine in their environment by modulating gene expression and exhibiting various phenotypes. For example, one of the most intensively investigated phenotypes following exposure of E. coli and S. Typhimurium to norepinephrine is enhanced bacterial growth in a serum-based medium. Host-pathogen investigations have demonstrated that the mammalian host utilizes nutritional immunity to sequester iron and prevent extraintestinal growth by bacterial pathogens. However, Salmonella and certain E. coli strains have a genetic arsenal designed for subversion and subterfuge of the host. Norepinephrine enhances bacterial growth due, in part, to increased iron availability, and transcriptional profiling indicates differential expression of genes encoding iron acquisition and transport proteins. Bacterial motility of E. coli and S. Typhimurium is also enhanced in the presence of catecholamines and increased flagellar gene expression has been described. Furthermore, epinephrine and norepinephrine are chemoattractants for E. coli O157:H7. In S. Typhimurium, norepinephrine enhances horizontal gene transfer and increases expression of genes involved in plasmid transfer. Exposure of E. coli O157:H7 to norepinephrine increases expression of the genes encoding Shiga toxin and operons within the locus of enterocyte effacement (LEE). Alterations in the transcriptional response of enteric bacteria to catecholamine exposure in vivo are predicted to enhance bacterial colonization and pathogen virulence. This chapter will review the current literature on the transcriptional response of E. coli and S. Typhimurium to catecholamines.