Micro-organisms are found in air, water and in the bodies of plants and animals.They may be unicellular or multicellular.

Micro-organisms are classified into four major groups. These groups are bacteria,fungi, protozoa and some algae.

Viruses are quite different from other micro-organisms. They reproduce only inside

Micro-organisms: Friend and Foe

Based on the significance, micro-organisms can be useful or harmful.

Uses Of Microorganisms

Protozoan cause serious diseases like dysentery and malaria.

Some bacteria and blue green algae present in the soil fix nitrogen from the atmosphere and convert into nitrogenous compounds.

Certain bacteria convert compounds of nitrogen present in the soil into nitrogen gas which is released to the atmosphere.

Pathogens: Some of the microorganisms cause diseases animals. Such disease causing microorganisms are called pathogens.

Cleaning of Environment: The microorganisms decompose dead organic waste
of plants and animals converting them into simple substances. These substances are again used by other plants and animals.

Microorganisms can be used to degrade theharmful and smelly substances and thereby clean up the environment.