Types of Microorganisms

By Ajay Anand


An organism which cannot be seen by naked eyes is called microorganism or microbe.

We need a microscope to see a microbe.


Bacteria have cell walls but do not have nucleus.

Some bacteria are autotrophs and some are heterotrophs.

Bacteria shapes: rod-shaped, spiral, spherical and comma-shaped.

Examples: Rhizobium, E. coli, Pseudomonas, Streptococcus, etc.


Algae are green plants which are simple in structure.

A cell of algae contains cell wall and chloroplast.

Algae are autotrophs. Some algae are microscopic.

Examples: Chlamydomonas, Spirogyra, etc.


Fungi have cell wall and nucleus in their cells but do not have chloroplast.

Fungi are saprotrophs, i.e. they feed on dead remains of plants and animals.

Almost all fungi are microscopic, except mushrooms.

Examples: yeast, Rhizopus (bread mould), Aspergillus, Penicillium, etc.



Protozoa do not have cell wall and chloroplast but they do have nucleus.

Examples: Amoeba and Plasmodium


Viruses are borderline case between living and non-living.

A virus behaves as non-living when it is outside a host cell.

Once it is inside a host, it behaves like a living being.

Examples: HIV, Tobacco Mosaic Virus (TMV), etc.

Habitat of Microorganisms

Microorganisms live almost everywhere on the earth.

They are found on land, water and in air.

They are even found inside and on our body.

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