BACTERIA

Bacteria are microscopic organisms. They are few micrometers in length.

NUTRITION:

Bacteria are heterotrophic. They cannot prepare their own food due to lack of chlorophyll. Although, some bacteria can prepare food, they are called autotrophic bacteria.

CLASSIFICATION:

On the basis of their shape, bacteria are classified into three groups:

* COCCI (Round shaped).

* BACILLI (Rod shaped).

* SPIRILLA (Spiral shaped):

STRUCTURE:

Bacteria have no nucleus. However, DNA is present. Cell wall and cell membrane both are present in such a way that cell wall lies outside and cell membrane lies inside.

METHODS OF OBTAINING FOOD:

As bacteria are heterotrophic, so they get their food in two ways:

(1) As parasites.

(2) As saprophytes.

* PARASITES:

These are the bacteria which get their food from other living organisms. They live in the bodies of other animals and plants here they produce toxic substances due to which diseases are produced in animals and plants.

Among human beings, bacteria produce diseases of plague, tetanus, diphtheria, pneumonia and cholera.

* SAPROPHYTES:

These are the bacteria which get their food fromthe bodies of dead organisms.

USES OF BACTERIA:

* They are used to convert milk into curd.

* Some bacteria are helpful in making cheese.

* Sugar cane juice produces vinegar with the help of bacteria.

* Due to bacteria, dead bodies and plants cause the fertility of soil due to the release of salts and minerals to soil.

* They are used for fermentation to manufacture baking products.