General microbiology and sterilisation: oxygen requirements: practice question

A Microbiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Microbiology · General microbiology and sterilisation: oxygen requirements

Sample item

In a tube of fluid thioglycollate medium, the organism grows as a narrow band a few millimetres below the surface, but neither at the very top nor at the bottom. What is its oxygen requirement?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. Microaerophilic

A band just below the surface shows that the organism needs reduced oxygen tension and is poisoned by full atmospheric oxygen, as with Campylobacter and Helicobacter. Obligate aerobes grow only at the top, obligate anaerobes at the bottom, and facultative anaerobes throughout the tube.

Option by option

  • A. Obligate anaerobic

    Obligate anaerobes would grow only in the deep, oxygen-free portion.

  • B. Obligate aerobic

    Obligate aerobes would grow only at the oxygen-rich top.

  • C. Facultative anaerobic

    Facultative anaerobes grow throughout the tube, densest at the top.

  • D. Microaerophilic (correct)

    Correct. A subsurface band indicates a microaerophile needing low oxygen.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is D, Microaerophilic. A band just below the surface shows that the organism needs reduced oxygen tension and is poisoned by full atmospheric oxygen, as with Campylobacter and Helicobacter.

Why is "Obligate anaerobic" not the answer?

Obligate anaerobes would grow only in the deep, oxygen-free portion.

Why is "Obligate aerobic" not the answer?

Obligate aerobes would grow only at the oxygen-rich top.

Why is "Facultative anaerobic" not the answer?

Facultative anaerobes grow throughout the tube, densest at the top.

What concept does this question test?

It tests General microbiology and sterilisation: oxygen requirements in Microbiology. Obligate aerobes grow only at the top, obligate anaerobes at the bottom, and facultative anaerobes throughout the tube.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study General microbiology and sterilisation: oxygen requirements?

Make a one-line identity card for each organism: shape and stain, defining test, toxin, disease and drug. Then use the flashcards and the other Microbiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.