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Cellular defenses against superoxide and hydrogen peroxide.
1Department of Microbiology, University of Illinois, Urbana, IL 61801, USA. jimlay@uiuc.edu
Annual Review of Biochemistry
|January 5, 2008
Summary
Early life evolved without oxygen, leading to vulnerabilities in microbes. Organisms developed oxygen tolerance by shedding sensitive enzymes and creating antioxidant defenses, which persist today.
Area of Science:
- Biochemistry
- Evolutionary Biology
- Microbiology
Background:
- Life originated in an anaerobic environment, shaping fundamental metabolic pathways without oxygen reactivity.
- The evolution of photosystem II led to a gradual increase in atmospheric oxygen, necessitating adaptations in early life forms.
Purpose of the Study:
- To review recent developments in understanding how early life adapted to increasing oxygen levels.
- To identify remaining puzzles regarding oxygen tolerance mechanisms in contemporary organisms.
Main Methods:
- Review of existing literature on microbial evolution and oxygen metabolism.
- Analysis of biochemical pathways and enzymatic mechanisms related to oxygen sensitivity and defense.
Main Results:
- Early microorganisms jettisoned oxygen-sensitive enzymes (e.g., those using glycyl radicals) and exposed iron-sulfur clusters.
- Microbes developed defense mechanisms against reactive oxygen species like superoxide (O(2)()) and hydrogen peroxide.
Conclusions:
- Contemporary organisms retain ancestral vulnerabilities and defenses related to oxygen metabolism.
- Bacteria serve as a key model system for investigating these evolutionary adaptations and ongoing research challenges.
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