What are the major groups of microorganisms?

Microorganisms are very small living organisms that cannot be seen with the naked eye. They are broadly classified into five major groups: bacteria, fungi, protozoa, algae, and viruses.

• Bacteria: Single-celled prokaryotes found everywhere. Some are useful in digestion and nitrogen fixation, while others cause diseases like cholera.
• Fungi: Can be unicellular (yeast) or multicellular (moulds, mushrooms). They help in making bread, alcohol, and medicines, but some spoil food and cause infections.
• Protozoa: Animal-like unicellular organisms such as Amoeba and Plasmodium. Some live freely in water, while others cause diseases like malaria.
• Algae: Plant-like organisms that perform photosynthesis. They produce oxygen and are used in food and industry.
• Viruses: Not truly living outside a host. They cause diseases such as influenza, HIV, and COVID-19 but are also used in vaccine research.

The five groups—bacteria, fungi, protozoa, algae, and viruses—play both helpful and harmful roles in our lives and environment.