Many bacterial species swim actively by means of flagella [1]. The flagella organelle is made of three parts: the basal body, the hook and the filament. The basal body consists of four rings (L,P,S, and M) mounted on a central rod. In Salmonella typhimurium and related organisms the rod has been shown [2] to consist of four different, yet evolutionary related proteins: in the distal portion of the rod there are about 26 subunits of protein flgG and in the proximal portion there are about 6 subunits each of proteins flgB, flgC, and flgF.

These four proteins contain in their N-terminal section a highly conserved asparagine-rich domain that we have used as a signature pattern.

This pattern is also found in:

• Flagella hook protein flgE from Gram-negative bacteria.
• Flagellar hook-associated protein 1 (HAP1) (flgK) from Gram-negative bacteria.
• Flagellar hook-basal body proteins flhO and flhP from Bacillus subtilis.
• The central section of the flagella core protein (flaA) of Borrelia burgdorferi.