Oxygen toxicity and the superoxide dismutase.

Area of Science:

• Microbiology
• Biochemistry
• Cellular Biology

Background:

• Oxygen is essential for aerobic life but can be toxic, generating reactive oxygen species.
• Superoxide radical (O(2)(-)) is a key mediator of oxygen toxicity.
• Enzymatic defenses, such as superoxide dismutase and catalase, protect cells from oxidative damage.

Purpose of the Study:

• To investigate the role of superoxide dismutase and catalase in bacterial defense against oxygen toxicity.
• To determine if superoxide dismutase induction confers resistance to hyperbaric oxygen and antibiotic-induced oxidative stress.

Main Methods:

• Comparing oxygen-induced changes in superoxide dismutase and catalase levels in Escherichia coli B and Bacillus subtilis.
• Assessing the resistance of induced and uninduced bacterial cells to hyperbaric oxygen.
• Evaluating the effect of streptonigrin, an antibiotic that generates superoxide radicals, on bacterial survival under aerobic conditions.

Main Results:

• Oxygen induced superoxide dismutase in E. coli B but not in B. subtilis.
• E. coli B with induced superoxide dismutase showed increased resistance to hyperbaric oxygen.
• B. subtilis catalase was induced by oxygen, while E. coli B catalase was not.
• Induced superoxide dismutase in E. coli B conferred resistance to streptonigrin lethality in the presence of oxygen.

Conclusions:

• Superoxide dismutase is a crucial defense mechanism against oxygen toxicity in bacteria.
• Catalase plays a secondary role in protecting against oxygen toxicity compared to superoxide dismutase.
• The ability to induce superoxide dismutase is important for bacterial survival under high oxygen conditions.