The number and distribution of flagella in bacterial cells is called flagellation. Based on the presence, absence, number and location of flagella, bacteria can be classified into following groups.
1. Atricus: Bacteria cells that do not have any flagella are called Atricus. For example- Bacillus diptheriae, Lactobacillus, Pasteurella, Corynebacterium diptheriae.
2. Monotrichous: Bacteria that have only one flagellum at one end of the cell are called monotrichous. For example, Vibrio cholerae.
3. Amphitrichous: Bacteria that have one flagella at both ends of the cell are called Amphitrichous. For example- Nitrosomonas, Spirillum.
4. Cephalotrichus: Bacteria that have a cluster of flagella at one end of the cell is called Cephalotrichus. For example, Pseudomonas aenoginosa, Pseudomonas fluorescens
5. Lophotrichous: Those bacteria that have a total of two sets of flagella at both ends of the cell are called Lophotrichous. For example- Spirillum minus, Pseudomonas.
6. Peritrichous: Bacteria whose entire cell is covered by flagella is called peritrichous. For example- Bacillus typhi, Escherichia coli, Salmonella typhi.