Concept preview

What you will be able to do

1. 01Label the parts of a prokaryotic (bacterial) cell and give the function of each.
2. 02Describe the three common bacterial shapes and how Gram staining sorts bacteria.
3. 03Explain the roles of extra structures such as flagella, pili, capsules and endospores.
4. 04Distinguish bacteria from archaea.

Bacteria are abundant, diverse prokaryotic organisms found in many habitats. Their cells lack a membrane-bound nucleus, and many have the small-cell organisation described in this lesson. Estimates of bacterial abundance in the human body are broadly comparable to human cell counts and vary between people and conditions. A common bacterial body plan is useful for study, but important exceptions exist.