Bacterial motility — terminology for flagellar arrangements In prokaryote morphology, what is the correct term for a cluster (tuft) of flagella emerging from one pole of a bacterial cell?

Introduction / Context:
The spatial arrangement of flagella on bacterial cells provides diagnostic clues to identification and influences motility patterns. Textbook terms distinguish between single and multiple flagella and whether they occur at one or both poles or around the entire cell surface.

Given Data / Assumptions:

• Monotrichous: one flagellum at a pole.
• Amphitrichous: a single flagellum (or tuft) at each of two poles.
• Lophotrichous: a tuft (cluster) of flagella at one pole.
• Peritrichous: flagella distributed around the cell surface.

Concept / Approach:
Precisely match the definition in the prompt (“cluster of polar flagella”) with established terminology. A tuft at a single pole defines lophotrichous arrangement. This differs from amphitrichous (poles on both ends), monotrichous (single), and peritrichous (all around). Correct usage aids in interpreting motility tests (for example, wet mount, semisolid agar) and species descriptions (for example, Pseudomonas often monotrichous; Spirillum species may be lophotrichous).

Step-by-Step Solution:
Note the keywords: “cluster” and “polar.”Map “cluster at one pole” to lophotrichous.Exclude amphitrichous (both poles) and monotrichous (single).Exclude peritrichous (flagella all around) and atrichous (no flagella).

Verification / Alternative check:
Illustrations in microbiology atlases consistently label tufts at one pole as lophotrichous; amphitrichous depicts opposite-end placement.

Why Other Options Are Wrong:

• Amphitrichous: implies poles at both ends, not a single polar tuft.
• Monotrichous: only one flagellum, not a cluster.
• Peritrichous: distributed over the entire surface.
• Atrichous: no flagella; not a tuft.

Common Pitfalls:
Interchanging lophotrichous with amphitrichous; remember “lopho-” suggests a tuft or crest at one location.

Final Answer:
Lophotrichous