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#aerobic bacteria

3 public questions tagged with this topic.

Microbial Physiology

What is the role of superoxide dismutase in aerobic bacteria?

Superoxide radical generated when flavoenzymes and respiratory chain components univalently reduce oxygen, highly toxic inactivating dehydratases bearing exposed iron sulfur clusters like aconitase and fumarase releasing free iron that fuels Fenton chemistry producing hydroxyl radical. Superoxide dismutase constitutes primary defense dismutating two superoxides into dioxygen and hydrogen peroxide reaction two O2 superoxide plus two protons to O2 plus H2O2. Enzymes classified by metal cofactor manganese SodA inducible by SoxRS, iron SodB constitutive, copper zinc SodC periplasmic exported via S

Ref: Brock Biology of Microorganisms, 16th ed., Chapter 6: Superoxide dismutase - ROS detoxification.

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Microbial Physiology

Which enzyme is crucial for breaking down hydrogen peroxide in aerobic bacteria?

Aerobic respiration inevitably leaks electrons to dioxygen generating superoxide and hydrogen peroxide. H2O2 is particularly hazardous because ferrous iron drives Fenton reaction producing hydroxyl radical that nicks DNA phosphodiester backbone, carbonylates proteins, and peroxidizes lipids. Aerobes counter with catalase, extraordinarily efficient heme tetramer with kcat approaching ten million per second, diffusion limited perfect enzyme. Active site ferriprotoporphyrin IX cycles between ferric resting state and Compound I oxoferryl radical after binding first H2O2, then reduced by second H2O

Ref: Madigan et al., Brock Biology of Microorganisms, 16th ed., Chapter 6: Oxidative stress - Catalase mechanism.

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