Bacterial flagellum is the organ of bacterial movement, Helicobacter pylori can pass through the mucus layer on the gastric epithelial cells from the strongly acidic gastric lumen to reach the neutral environment of the gastric epithelial cells, which is a good example of the role of flagellar movement, through flagellar staining can be observed flagellar morphology, the number of flagellum and flagellum in the distribution of the location of the bacteria, the number of flagellum and distribution of the location of flagellum in the bacterial body is one of the important bases of identification of the bacterial body.

Flagellar staining methods include modified Ryu method, carbolic acid red method, Leifson method, silver staining method, Loffler method, Cerares-Gill method and so on. Flagellar staining solution (Cerares-Gill method), also known as Cesar-Kill staining method, is mainly applied to the bacterial flagellum that is not easy to stain, plant pathogenic bacteria that produce more gelatin, and bacteria whose flagellum is very fine and easy to fall off.