Further investigation of the mechanism of <Emphasis Type="Italic">Vitreoscilla</Emphasis> hemoglobin (VHb) protection from oxidative stress in <Emphasis Type="Italic">Escherichia coli</Emphasis> |
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Authors: | Meltem Yesilcimen Akbas Tugrul Doruk Serhat Ozdemir Benjamin C Stark |
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Institution: | (1) Department of Biology, Inonu University, Malatya, 44069, Turkey;(2) Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel;(3) Biology Division, Department of Biological, Chemical, and Physical Sciences, Illinois Institute of Technology, Chicago, IL, USA |
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Abstract: | In Escherichia coli, Vitreoscilla hemoglobin (VHb) protects against oxidative stress, perhaps, in part, by oxidizing OxyR. Here this protection, specifically
VHb-associated effects on superoxide dismutase (SOD) and catalase levels, was examined. Exponential or stationary phase cultures
of SOD+ or SOD−
E. coli strains with or without VHb and oxyR antisense were treated with 2 mM hydrogen peroxide without sublethal peroxide induction, and compared to untreated control
cultures. The hydrogen peroxide treatment was toxic to both SOD+ and SOD− cells, but much more to SOD− cells; expression of VHb in SOD+ strains enhanced this toxicity. In contrast, the presence of VHb was generally associated in the SOD+ background with a modest increase in SOD activity that was not greatly affected by oxyR antisense or peroxide treatment. In both SOD+ and SOD− backgrounds, VHb was associated with higher catalase activity both in the presence and absence of peroxide. Contrary to its
stimulatory effects in stationary phase, in exponential phase oxyR antisense generally decreased VHb levels. |
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