Responses to Reactive Oxygen Species in Escherichia Coli: The Roles of Aconitase a and Fur Protein

Varghese, Shery Mathew

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Description

Title

Responses to Reactive Oxygen Species in Escherichia Coli: The Roles of Aconitase a and Fur Protein

Author(s)

Varghese, Shery Mathew

Issue Date

2007

Doctoral Committee Chair(s)

James Imlay

Department of Study

Microbiology

Discipline

Microbiology

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Biology, Cell

Language

eng

Abstract

The Fur regulon is a well-characterized regulon that monitors intracellular iron concentrations by monitoring concentrations of the ferrous ion. We observed that sub-micromolar concentrations of H2O2 in vivo can cause E. coli catalase and NADH peroxidase mutants (Hpx -) to lose control of their intracellular iron pools. This concentration of H2O2 was sufficient to activate the fur regulon in vivo and cause induction of iron-import proteins. This would potentially result in an increased rate of H2O2-mediated Fenton damage. However, induction of fur expression by OxyR restored Fur repression in iron-replete media. Indeed, when the OxyR binding site upstream of fur was disrupted, Hpx- mutants accumulated high concentrations of intracellular free iron and suffered mutagenesis and bacteriostasis. These defects were eliminated by mutations or chelators that slowed iron import, confirming that dysregulation of iron uptake was the root problem. Collectively these data show the importance of controlling free iron levels intracellularly under oxidative stress.

Graduation Semester

2007

Type of Resource

text

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