Answer: (A) amphitrichous

Bacteria with two or more flagella at one or both ends are classified as amphitrichous. This arrangement allows enhanced motility by enabling directional changes through activation of flagella at either pole.​

Option Explanations

• (A) Amphitrichous: Correct. Features one or more flagella (often two or more) at both poles or one pole, aiding reversal of movement; examples include Campylobacter jejuni and Alcaligenes faecalis.​

• (B) Peritrichous: Flagella distributed over the entire cell surface (except poles), as in Escherichia coli, for omnidirectional propulsion.​

• (C) Lophotrichous: Tuft of flagella at one end only (polar bundle), like in Helicobacter pylori, for rapid forward swimming.​

• (D) Atrichous: No flagella present, resulting in non-motile bacteria such as Corynebacterium.​

Introduction: Bacteria with Two or More Flagella at One or Both Ends
Amphitrichous bacteria with two or more flagella at one or both ends represent a key flagellar arrangement in microbiology, enabling precise motility in diverse environments. This configuration distinguishes them from other types like peritrichous or lophotrichous bacteria. Understanding these helps in exams and research on microbial movement.​

Flagella Arrangements in Bacteria
Bacterial flagella drive locomotion via rotary motion. Major types include:

• Amphitrichous: 2+ flagella at poles for bidirectional travel.​

• Peritrichous: Flagella all over the body for swarming.​

• Lophotrichous: Bundle at single pole for fast directional motility.​

• Atrichous: Lacking flagella, relying on gliding or other means.​

• Monotrichous: Single flagellum at one end.​

Amphitrichous Bacteria Characteristics and Examples
These bacteria switch active flagella for quick turns, ideal for viscous habitats or host colonization. Common examples: Campylobacter jejuni (foodborne pathogen) and Aquaspirillum serpens. Lab observation via motility tests confirms this type.​