Explain how a bacterial cell can be distinguished from cells of organisms in other kingdoms.

Bacteria are usually very small: their size does not exceed 10 microns. They do not have a nuclear envelope, a single chromosome is often ring-shaped and is located directly in the cytoplasm of the cell.
Inside the bacteria, there are no organelles surrounded by membranes, that is, there is no endoplasmic reticulum (its role is played by numerous protrusions of the cell membrane), mitochondria, and plastids. Ribosomes are small.
Prokaryotic cells are covered with a capsule that protects bacteria from damage and drying out.