Escherichia coli is a facultative anaerobic bacterium because it can

Correct answer: C. survive without oxygen, but uses oxygen if it is present.

  • A. not survive in the presence of oxygen.
  • B. utilise low concentration of oxygen only.
  • C. survive without oxygen, but uses oxygen if it is present.
  • D. neither use oxygen for its growth nor can be harmed by it.

Explanation

A facultative anaerobe, such as Escherichia coli, can grow in both aerobic (with oxygen) and anaerobic (without oxygen) environments. However, it thrives better when oxygen is available because it can generate more energy through aerobic respiration than anaerobic processes. Therefore, it does not require oxygen but will use it if present, which makes Option C correct. Option A is incorrect because Escherichia coli can indeed survive in oxygen. Option B is incorrect as facultative anaerobes are not limited to low concentrations of oxygen. Option D describes aerotolerant organisms, which makes it incorrect for this question.

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