There are many kinds of
microorganisms present in the universe. They are broadly classified into the
Bacteria: They are unicellular prokaryotic organisms or simple association of similar cells.
Cell multiplication usually happen by binary fission.
Example: Escherichia coli, Bacillus subtilis
Fungi: They are eukaryotic organisms which is devoid of chlorophyll. They are usually multicellular.
They range in size and shape from single celled microscopic yeasts to giant
multicellular mushrooms and puffballs.
Example: Aspergillus niger, Agaricus bisporus
Protozoa: They are unicellular eukaryotic organisms. Their role in nature are varied. The best
known protozoa cause disease in human beings and animals.
Example: Giardia lamblia, Plasmodium vivax
Algae: They range from unicellular, colonial to multicellular forms. All algal cell contain
chlorophyll and are capable of photosynthesis. They are found most commonly in
aquatic environments and damp soil.
Example: Spirogyra, Chlamydomonas
Viruses: In the study of Microbiology, we encounter “organisms” which may represent the borderline of
life. Viruses are simpler in structure and composition than other living cells.
A virus is made up of nucleic acids and proteins. Viruses are obligate
parasites. They grow only within an appropriate host cell (plant, animal,
humans or microbe). They cannot multiply outside a host cell.
Example: HIV, Rabies virus