Which term is applied for certain microbes that can thrive without oxygen?

Appeared in: MNS 2015

Explanation

Anaerobes are microorganisms that can survive and grow in environments lacking free oxygen.
They utilize alternative metabolic pathways like anaerobic respiration or fermentation to produce energy.
This group includes organisms for whom oxygen is toxic (obligate anaerobes) and those that can switch between aerobic and anaerobic metabolism (facultative anaerobes).

Option A: Aerobes are organisms that require oxygen for cellular respiration and cannot survive without it. This is the opposite of the condition described in the question.
Option B: Fungi represent a large kingdom of eukaryotic organisms. While some fungi, like yeast, can be facultative anaerobes, most are aerobic. The term is a broad biological classification, not a specific term based on oxygen requirement.
Option D: Algae are typically photosynthetic aquatic organisms. They produce oxygen as a byproduct of photosynthesis and require it for respiration. They are not defined by an ability to live without oxygen.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Microbial classification based on oxygen requirements as background academic context rather than a clinical decision trigger.
Understanding anaerobes is critical for nurses, as they cause serious infections like tetanus (Clostridium tetani), gas gangrene (Clostridium perfringens), and deep-seated abscesses.
Nursing care for deep wounds (e.g., punctures, bites) or abscesses often involves debridement and cleaning to eliminate the anaerobic environment where these bacteria flourish.
Specimen collection for suspected anaerobic infection requires special anaerobic transport media and techniques to prevent oxygen exposure, which could kill the target organisms and lead to a false-negative result.

How to Approach the Question

First, identify the key phrase in the question stem: 'thrive without oxygen'.
Break down the terminology. The prefix 'an-' means 'without', and 'aero' refers to air or oxygen. Thus, 'anaerobe' literally means 'without air'.
Evaluate each option based on this understanding.
Option A, 'Aerobes', require oxygen, making it the direct opposite of the correct answer.
Option C, 'Anaerobes', do not require oxygen, which perfectly matches the question's description.
Options B ('Fungi') and D ('Algae') are broad classifications of organisms, not specific terms defining their relationship to oxygen. While some fungi are anaerobic, the term itself is not the definition. Therefore, 'Anaerobes' is the most precise and correct term.

Concept Tested & Keywords

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E6 Medicine Harrison 22e Part 1 p. 1412-1414

Practise the full MNS 2015

Attempt every question from this paper in a timed mock, then review the full solution for each one.