Courses for Kids
Free study material
Offline Centres
Store Icon

Types of Microorganisms

share icon
share icon

What are Microorganisms?

A living being is considered when it has the ability to reproduce, respond to environmental stimuli, and constitutes a living organism. All living organisms need sustenance to survive, hence they require nutrient supplements. To obtain food mobility plays a major role in an organism. 

The majority of the organisms are visible to us. In these, few are extremely small and can only be visible to us through a microscope. These are known as microorganisms and are single-celled or unicellular. These are present in every habitat and are ubiquitous. These play a major role in maintaining the ecological balance. These dwell inside the body and around every organism. These are helpful in the maintenance of the health of organisms and even clean the outside environment. These participate in food production also.

On the other hand, microorganisms are responsible for various dreadful diseases. For example, we witness the growth of fungus on bread when left unused for a couple of days. The reason being moist in the bread, making it one of the most favourable conditions for the breeding of microbes.

Classification of Microorganisms

Microorganisms are categorized into four major groups:

  • Bacteria: These are microscopic, single-celled organisms that grow in diverse environments. These organisms can live in soil, the ocean, and also in the human gut. These act in a positive way by participating in curdling milk into yoghurt and helping in digestion.

  • Fungi: These are a group of microorganisms that are eukaryotic in nature and these consist of microorganisms such as yeasts, moulds and mushrooms. These are grouped into a kingdom and are different from other eukaryotic life kingdoms of plants and animals.

  • Algae: These are simple, non-flowering, and typically aquatic plants of a huge group that have seaweeds and many single-celled forms included in them. Algae has chlorophyll in it but lacks true stems, roots, leaves, and vascular tissue. Algology or Phycology is the study of algae and it has a range of photosynthetic organisms and many are not closely related. They are a polyphyletic group. 

  • Protozoa: Protozoa (also protozoan, plural protozoans) is an informal term for single-celled eukaryotes, either free-living or parasitic, which feed on organic matter such as other microorganisms or organic tissues and debris.

Apart from the above microorganisms, viruses are microscopic but differ in their reproduction aspects as these reproduce only in cells of their hosts. The host organisms are animals, bacteria, or plants.

Useful Microorganisms

  • These are mainly used in the baking industry for the preparation of cakes, bread, pastry, etc.

  • Mainly used in the production of milk products. Example: In the formation of curd from the milk, lactobacillus bacteria is used 

  • These are used in the production of alcohol.

  • This is used in the preparation of organic acids such as citric acid, lactic acid, fumaric acid, gluconic acids.

  • Steroids are prepared by using microorganisms.

  • Vitamins are also produced with the microorganisms such as Vitamin B complex or Riboflavin by Ashbya gossypii, Eremothecium ashbyii and Clostridium bytyricum. A known Vitamin C or Ascorbic acid is produced by species Acetobacter.

  • Enzymes such as lipase, lactase, amylase, pectinase, penicillinase are synthesized by microorganisms.

  • The soil fertility is increased by the microorganisms and by fixing nitrogen.

  • Used in pest control.

Harmful Microorganisms

  • Microorganisms grow on food and spoil it. 

  • Some pathogens are transmitted directly from an infected person.

  • Through air, water and food, the pathogens can enter our bodies easily

  • Pathogens cause diseases in living beings 

  • Diseases Caused By Microorganisms

Some Diseases Caused By Microbes are:








Flu & Common cold


Athlete’s foot





Chagas disease



Tinea versicolor

Sleeping sickness

Herpes and cold sores



Intestinal protozoan disease




Lyme disease



Diseases Caused By Microorganisms in Animals



Anthrax diseases

Bacillus anthracis

Foot and Mouth disease


Diseases Caused By Microorganisms in Plants



Citrus canker


Rust of wheat


Yellow vein mosaic of Okra



Affect on Food By Microorganisms

Microorganisms affect the food which results in food spoilage where the quality of food is damaged and makes it unsuitable for human consumption. The main microorganisms which are responsible for food spoilage are Bacteria, moulds, and yeast. These produce certain enzymes which decompose the important constituents of food. Moulds are responsible for the spoilage of food with reduced water activity. For eg.: Dry cereals, Cereal products.

Bacteria can be a reason for the spoilage of food with increased water activity. For eg., milk products.

Interesting Facts About Microbes

  • 1.82kgs of your body’s weight constitutes the collective weight of microbes in your body

  • Microbes can be fatal.

  • There are more than a billion microbes in a person’s mouth

  • Your belly button alone has more than 1400 bacteria

  • Dry hands have fewer bacteria than damp hands

  • The smallest known bacteria is the Mycoplasma

  • 50% of the oxygen we breathe come from microbes

  • Microbes in our gut cause a change in mood

Want to read offline? download full PDF here
Download full PDF
Is this page helpful?

FAQs on Types of Microorganisms

1. Are Microorganisms a Friend or Foe?

Ans - Most microorganisms are beneficial, for example, there are microorganisms in our large intestine that synthesis vitamins and allow them to be absorbed into the bloodstream. A minority are pathogens (disease-causing agents).

2. What are the Sites of Carriage of Microorganisms?

Ans - Sites of carriage:

  • Nasal: Staphylococcus aureus.

  • Nasopharyngeal: Meningococcus, Bordetella.

  • Urinary: Salmonella.

  • Faecal: Salmonella.

  • Serum: Hepatitis B.

  • Hands: Klebsiella, Pseudomonas, Staphylococcus.