Four types of bacteria on the basis of their shape are:
- Coccus — These are spherical or ovoid in shape.
- Bacillus — These are rod-shaped. They may occur singly or in groups of two or three, joined end to end in long chains.
- Spirillum — These are spiral-shaped bacteria.
- Vibrio — These are comma-shaped bacteria. For example, Vibrio cholerae.