Abstract
Iron is required for bacterial growth because it serves as a co-factor for enzymes involved in DNA synthesis, cellular respiration, and other processes. Disrupting bacterial iron homeostasis is an effective strategy to prevent the growth of antibiotic-resistant bacteria, and gallium (Ga³⁺) has emerged as a promising candidate due to its ability to displace iron (Fe³⁺) and prevent essential iron-dependent pathways. However, Escherichia coli are naturally less sensitive to gallium than many other bacteria, and the mechanisms that control gallium tolerance are not completely understood. To address this, we performed a genome-wide transposon sequencing (TnSeq) screen to identify genes important for the survival of a pathogenic E. coli isolate (M12) in gallium nitrate. The TnSeq results indicated that inactivation of enterobactin siderophore-related genes (entS, fepD, ybeZ) enhances bacterial survival in gallium, while disrupting the ferric dicitrate transport system increases susceptibility. We validated these findings through targeted gene knockouts and gallium sensitivity experiments. Our findings suggest that enterobactin can complex with gallium for cellular uptake, but that the ferric citrate receptor FecA can discriminate between gallium citrate and iron citrate. Expression of fecA increased with gallium exposure, showing that gallium induces FecA-mediated iron uptake. Gallium also increased intracellular levels of manganese in the ΔfecA strain. Supplementation with iron or manganese restored growth of M12 ΔfecA in gallium, suggesting that gallium sensitivity is linked to both iron starvation and oxidative stress. As the ferric dicitrate transport system is an important virulence factor in several extraintestinal infection sites, our results suggest that targeting FecA may increase E. coli susceptibility to gallium while also suppressing virulence.
Degree
MS
College and Department
Life Sciences; Microbiology and Molecular Biology
Rights
https://lib.byu.edu/about/copyright/
BYU ScholarsArchive Citation
Parveen, Nagama, "Opposing Roles for Iron Transport Systems in Gallium Tolerance in Extraintestinal Pathogenic Escherichia Coli" (2025). Theses and Dissertations. 11055.
https://scholarsarchive.byu.edu/etd/11055
Date Submitted
2025-08-04
Document Type
Thesis
Keywords
gallium, iron transport, ferric dicitrate, FecA, mastitis-associated E. coli, ExPEC
Language
english