Basic Structure of Bacteria

 

Bacteria Discovery

 

Bacteria was discovered by A.V. Leuwenhoek in 1676.

 

 

Structure of Bacteria

 

Bacteria are smallest and simplest living organism measures from 0.2m to 2 micron in breadth and 2 to 10 micron in length. They are strictly unicellular but some species remain associated with each other alter cell division and form colonies.

 

A generalized bacterial cell consists of following structures.

 

1- Flagella

 

They are extremely thin appendages, which originate from basal body, a structure in the cytoplasm beneath cell membrane. Flagella help in bacterial locomotion.

 

2- Pilli

 

They are hollow, filamentous flagella like appendages, which help in conjugation but not in locomotion.

 

3- Capsule

 

It is a protective sheath made up of polysaccharides and proteins. It provides greater pathogenicity and protects bacteria against phagocytosis.

 

4- Cell Wall

 

Bacterial cell wall mostly made up of amino acids, sugar and chitin. It surrounds the cell membrane, determine shape and protects bacteria from osmotic Iyses. Most bacteria have a unique macromolecule called Peptidoglycan in addition to it. Sugar molecules, teichoic acid, glyco proteins and lipo polysaccharide are also present.

 

5- Cell Membrane

 

It is present inside the cell wall attached to it at few places containing many pores.

 

It is made up of lipids and proteins.

 

It acts as a respiratory structure.

 

6- Cytoplasm

 

Bacterial cytoplasm is granular containing many small vacuoles, glycogen particles and ribosomes.

 

7- Mesosomes

 

These are the invaginations of the cell membrane into the cytoplasm.

 

They are in the form of vesicles, tubules or lamella.

 

They help in the DNA replication, cell division, respiration and export of enzyme.

 

8- Hereditary Material

 

Bacterial hereditary material DNA is found as concentrated structures called Bacterial chromosomes or

chromatin bodies. It is mostly scattered in the cytoplasm.

 

A small fragment of extra chromosomal circular DNA, called Plasmid is also present.

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