The distinctive shapes of different bacterial cells are important for their identifyication. Bacteria can take a range of shapes, including: Bacillus (Rod), Coccus (spherical), Spirllum (corkscrew) and Vibrio.
Other factors used for identification of bacteria includes arrangement, colours, cell wall presence and selectivity of growth medium. All these features effect how we can treat bacterial infections. For example, penicillin obstructs the construction of a cell wall, making it effective against cells that have them, but not those that don’t.