Shape

The simplest classification system of bacteria is based on their shape and arrangement. Bacteria come in sphere, rod, spiral, comma and filament shapes, and can be paired up in twos, strings or 3D shapes. Using the diagram, can you figure out what Staphylococcus aureus, Vibrio cholerae and Streptococcus sp. look like?

Gram test

Amongst bacteria, the cell wall composition is a key determinant of what type they belong to. This is important in terms of predicting their response to various antibiotics. Based on different bacteria species’ response to crystal violet stain, Gram positive bacteria are able to take up the stain and appear violet under a microscope, while Gram negative bacteria do not take the stain up and will appear…