Which statement best describes the oxidase test results for aerobic bacteria?

Which statement best describes the oxidase test results for aerobic bacteria?

• A. It cannot respire.
• B. It performs fermentation only.
• C. It uses anaerobic respiration exclusively.
• D. It is oxidase-positive and uses aerobic respiration with cytochrome c oxidase.

Answer: (D)

The oxidase test checks whether bacteria have cytochrome c oxidase, an enzyme in the electron transport chain that transfers electrons to oxygen during aerobic respiration. A positive result means cytochrome c oxidase is present, so the organism uses aerobic respiration with this enzyme, typically turning the test reagent a dark color quickly. For aerobic bacteria, this is the best description because they rely on oxygen as the terminal electron acceptor and many possess cytochrome c oxidase as part of their respiratory chain. The other notions—that the organism cannot respire, that it relies only on fermentation, or that it uses anaerobic respiration exclusively—don’t fit the general behavior of aerobes and don’t reflect what the oxidase test measures.

The oxidase test checks whether bacteria have cytochrome c oxidase, an enzyme in the electron transport chain that transfers electrons to oxygen during aerobic respiration. A positive result means cytochrome c oxidase is present, so the organism uses aerobic respiration with this enzyme, typically turning the test reagent a dark color quickly.

For aerobic bacteria, this is the best description because they rely on oxygen as the terminal electron acceptor and many possess cytochrome c oxidase as part of their respiratory chain. The other notions—that the organism cannot respire, that it relies only on fermentation, or that it uses anaerobic respiration exclusively—don’t fit the general behavior of aerobes and don’t reflect what the oxidase test measures.