Identification of E. coli Core and Uropathogen-specific Genes Involved in Adaptation to Copper Stress

Abstract

Urinary Tract Infections are a global health concern affecting approximately 7-11 million people in the United States annually. Uropathogenic Escherichia coli (UPEC) are the primary etiologic agent of uncomplicated UTIs, accounting for ~80% of infections in otherwise healthy women. With antimicrobial resistance on the rise for most pathogens, including UPEC, understanding mechanisms of bacterial immune evasion is paramount to developing novel therapeutics. We sought to characterize E. coli core and uropathogen-specific genes involved in mitigation of copper toxicity, a known host immune effector. To accomplish this, we conducted a genome-wide screen of a commensal E. coli mutant library and comparative transcriptomic profiling of UPEC to identify copper-responsive genes. We identified two arms of iron homeostasis, namely ferric-enterobactin uptake and ferrous iron transport, as playing a role in adaptation to copper stress. Here we proposed a model for enterobactin-mediated iron homeostasis as necessary to maintain adequate cellular iron levels to potentially outcompete copper and prevent mismetallation of key metalloenzymes. On the other hand, we identified FeoB, an inner membrane Fe²⁺ permease, to contribute to increased copper accumulation and stress in a commensal strain. However, our UPEC strain did not share this phenotype and may have adapted either FeoB or the genetic regulation of the encoding gene to limit FeoB-mediated copper accumulation. Collectively, our research highlights the complex and dynamic nature of bacterial metal homeostasis and begs for further research into the interplay between iron acquisition and copper toxicity. These studies provide novel insights into E. coli core and pathogen-specific copper response. Our findings have the potential for numerous future studies which will lead to a greater understanding of host-pathogen interactions, providing novel targets for UTI therapeutics and preventatives.