A cluster of polar flagella is called?

Appeared in: SJH Nursing Officer - 2019

Explanation

Lophotrichous describes the arrangement where a bacterium has a tuft or cluster of multiple flagella originating from one pole (end) of the cell.
The term comes from the Greek words 'lopho' (meaning tuft or crest) and 'trichous' (meaning hair), literally translating to 'crest of hair'.
This arrangement provides powerful, directional propulsion for the bacterium.
The provided image visually confirms this definition, showing a bacterium with a bundle of flagella at one end labeled as 'Lophotrichous'.

Option B: Amphitrichous describes bacteria that have flagella at both opposite poles, not a cluster at a single pole. 'Amphi-' means 'on both sides'.
Option C: Monotrichous refers to a single flagellum at one pole. 'Mono-' means 'one'. The question specifies a 'cluster' of flagella.
Option D: Peritrichous describes flagella that are distributed all over the surface of the bacterium, not just at the poles. 'Peri-' means 'around'.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Bacterial classification based on flagellar arrangement as background academic context rather than a clinical decision trigger.
In clinical microbiology, identifying the flagellar arrangement is a key step in the classification and identification of bacterial species.
Bacterial motility, enabled by flagella, is a significant virulence factor. It allows pathogens to move towards nutrients (chemotaxis), invade host tissues, and escape the host's immune response.
The 'swarming' motility of Proteus species on agar plates, due to their peritrichous flagella, is a characteristic diagnostic feature observed in the lab.

How to Approach the Question

This is a factual recall question based on microbiology terminology.
First, identify the key terms in the question: 'cluster' and 'polar flagella'.
Next, analyze the prefixes of the options to understand their meanings: 'Lopho-' (tuft/cluster), 'Amphi-' (both sides), 'Mono-' (one), and 'Peri-' (around).
Match the definition from the question to the correct prefix. 'Cluster' corresponds to 'Lopho-'.
'Polar' confirms the location is at an end of the cell.
Combine these parts: Lophotrichous means a cluster of flagella at a pole, which directly answers the question.

Concept Tested & Keywords

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E6 Microbiology Essentials Sastry 4e Part 1 pp. 38-40, 39-41

Practise the full SJH Nursing Officer - 2019

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