Site author Richard Steane
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Bacterial cell structure

Escherichia coli (E.coli)
- a "colo(u)rized scanning electron micrograph
(SEM)" from CDC Atlanta
Click above for the internal details
Bacteria consist of single cells. They are much smaller than animal or plant cells.

These cells have several similarities with cells of (green) plants and animals, but lots of differences, which is why they are put into a kingdom of their own.

On the outside of the cell is a cell wall, but it is not usually made of cellulose.

Inside this is a membrane enclosing the cytoplasm.

The genetic material is not enclosed in a nuclear membrane like higher plants and animals. The main genetic material is DNA, in a diffuse blob, loose in the cytoplasm. Also in the cytoplasm there may be other loops of DNA which are called plasmids. This plasmid DNA is likely to contain genes for other characteristics.

There are no mitochondria in bacterial cells. In fact they are about the same size as one another.

Likewise, there are no chloroplasts in bacterial cells.

Bacterial cells do contain ribosomes, but they are slightly smaller than ribosomes in animal and plant cells.

Staphylococcus aureus

Approximate sizes:

in micrometres (Ám) also known as microns
[1Ám = 0.001mm = 0.000001m (10-6m)]

cell/component size / Ám
E. coli cell length 2
E. coli cell width 0.5
Staphylococcus aureus cell diameter 0.6
bacterial ribosome 0.020 (20nm)

What you should know

A bacterial cell consists of cytoplasm and a membrane surrounded by a cell wall;
the genes are not in a distinct nucleus;
some of the genes are located in circular structures called plasmids.

Notes on words:

Bacterium is singular, bacteria plural.

Bacterial is an adjective, meaning to do with bacteria.

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