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In this article we will discuss about the Structure of Bacterial Cell.
Bacteria (sing. bacterium) are unicellular prokaryotic microorganisms which divide by binary fission. They do not possess nuclear membrane and the nucleus consists of a single chromosome of circular double-stranded DNA helix (Fig. 1.1).
Flagella:
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These are long filamentous, cytoplasmic appendages, 12-30 μm in length, protruding through the cell wall and contain contractile protein flagellin. These are organs of locomotion.
Fimbriae or pili:
These are thin, short filaments (0.1-1.5 μm x 4 to 8 nm) extruding from the cytoplasmic membrane, also called pili. They are made of protein (pilin).
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Capsule:
It is an outer covering of thin jelly-like material (0.2 μm in width) that surrounds the cell wall. Only some bacterial species possess capsule. Capsule is usually made of polysaccharide (e.g. pneumococcus), occasionally polypeptide (e.g. anthrax bacilli) and hyaluronic acid (e.g. streptococcus).
Cell wall:
It is a tough and rigid structure of peptidoglycan with accessory specific materials (e.g. LPS, teichoic acid etc.) surrounding the bacterium like a shell and lies external to the cytoplasmic membrane. It is 10-25 nm in thickness. It gives shape to the cell.
Nucleus:
The single circular double-stranded chromosome is the bacterial genome. Other structures include cytoplasmic membrane, mesosomes, ribosomes and cytoplasmic inclusions. Unlike eukaryotes cytoplasm does not contain ribosome, Golgi, cytoskeleton.
