amphitrichous

Amphitrichous is a term used in microbiology to describe a bacterial flagellar arrangement in which flagella are located at both ends of the cell. The name derives from Greek amphi- meaning "both" and trichos meaning "hair."

In amphitrichous bacteria, flagella may be singular at each pole or there may be several flagella at both poles, forming small tufts. The arrangement supports locomotion by rotating the flagella, enabling the cell to swim forward, reverse direction, or reorient. The specific swimming patterns depend on the number, position, and rotation of the flagella.

Spirillum volutans is a classic example of amphitrichous bacteria. Amphitrichous organization also occurs in other aquatic and soil bacteria, reflecting adaptations to motility in viscous or heterogeneous environments.

Identification and study: The arrangement is determined by microscopy after specialized staining or by genetic and structural analyses. Amphitrichous bacteria are distinguished from monotrichous (one flagellum at a single pole), lophotrichous (tufts at one pole), and peritrichous (flagella distributed over the cell surface).