Bacterial flagella are much simpler than undulipodia, being hollow cylinders about 15 nm in diameter, consisting of subunits of a protein (flagellin) arranged in helical spirals.

• 细菌鞭毛比UNDULIPODIA简单很多，它是由含有螺旋排列的蛋白质亚单位（鞭毛蛋白）组成的，直径约15nm的中空圆柱体。