Figure 1. Distinctive placement of bacterial flagellum.

(A) Bacteria with flagella distributed all over the cell (e.g. Escherichia coli) are peritrichous. (B) Monotrichous bacteria, such as Vibrio cholera, Pseudomonas aeruginosa, and Caulobacter crescentus have a single flagellum present at one end of the cell. (C). Spirochetes, including species of Borrelia, Treponema, and Leptospira, possess specialized flagella located within the periplasmic space. The rotation of the periplasmic flagella allows this bacterium to swim forward in a corkscrew-like motion.