bacteria and its types

 Bacteria

Bacteria are minute, microscopic, prokaryotes. They are undifferentiated, unicellular organisms which are usually identified by their specific activities, more than their general organization.

Occurrence: Bacteria are omnipresent, occurring in every conceivable environment. They occur in water, in air, in soil, and inside the body of living organisms. There are bacteria which occur in hot springs of water as well as in extreme cold temperature.

Size: The average size of bacterial cell ranges from 1micro meter to 10 micro meter in length and about 0.7 mm to 1.5mm in width. 

Shape: The bacteria generally exhibit a fairly constant shape and form. However, some of them are capable of changing their body shape and size in accordance with the environmental influence, such bacteria are called pliomorphic.

Fallowing are the some common types of bacteria based on their shape.

1. Cocci: They are spherical in shape. They can be further distinguished into

• Monococcus, which occur singly
• Diplococcus, which occurs in pairs
• Tetracoccus, which occur in groups of four
• Streptococcus, which occurs in the form of a filament and 
• Staphylococcus, which occurs in the form of sheets

Some cocci may occur in cubical packets of eight or more cells, they are known as sarcina.

2. Bacilli: They are straight, cylindrical, rod shaped bacteria. They may be further distinguished into fallowing.

• Monobacillus, which occurs in single
• Diplobacillus, which occurs in pairs
• Streptobacillus, which occurs in filament form and 
• Palisade Bacillus, which occurs in the form of stack

3. Spirilli: These bacteria are spirally coiled like a cork screw.

4. Vibrio: These are elongated, C shaped or comma shaped bacteria.

Most of the bacteria contain one to many locomotive structure called flagella. Cocci do not have flagella. Based on the number and mode of attachment of the flagella, bacteria can be distinguished into the following types:

• Atrichous: Bacteria without flagella are known as Atrichous.
• Monostrichous: Bacteria with a single flagella at one end are known as Monotrichous Bacteria.
• Cephalotrichous: Bacteria with many flagella attached at one end.
• Amphitrichous: Bacteria with a single flagella at each end.
• Lophotrichous: Bacteria with a group of flagella attached at each end.
• Peritrichous: Bacteria with flagella all over the body.

On the bases of the differential staining or gram staining technique the bacteria are classified into two types, they are 

1. Gram positive: The bacteria which retain purple colour. 
2. Gram negative: The bacteria which lose purple colour.