Picture of Bacterial Cell, Diagram of a Generalised Composite Bacterial Cell showing Gram +ve & Gram -ve types (graphic)

CELL WALL: The orange layer is peptidoglycan which lies just exterior to the plasma membrane (blue).

S-LAYER: The bacterium may be covered by a regular arrangement of proteins called an S-layer; ref: Journal of Bacteriology, Jan 1998, p. 52-58. In this diagram, the proteins are shown as an array of silvery spheres lying on top of the peptidoglycan layer.

CAPSULE: The capsule (yellow) is made from poly-D-glutamic acid (whereas most bacterial capsules are made from polysaccharides). Capsules are required to make the anthrax bacteria virulent.

GENOME: The genetic material is a skein of circular DNA localised as the nucleoid. The nucleoid lacks a nuclear membrane (a defining characteristic of prokaryotic cells). Peeping out from the upper right part of the nucleoid is a plasmid - a separate piece of DNA.

CYTOPLASM: The bacterial cytoplasm is shown filled with ribosomes. These are somewhat smaller than their eukaryotic counterparts and many are shown linked into polysomes.


The picture shows a cutaway of the anthrax bacterium, Bacillus anthracis, with many of the main components illustrated. This is the vegetative form as it might occur in the body. In this state, the bacterium does not form spores. It may exist as an individual bacterium or be grouped into short chains. The image above is 300 pixels across and the original is 1,712 pixels across and lacks all labels. Anthrax is a potential bioterror agent. It has been used as a bioweapon and is one of several potential biological weapons agents such as smallpox. Please see the CDC site.

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