Microbes and Human Welfare Class 12 Notes

Microbes and Human Welfare Class 12 Notes: A microbe is the Smallest living thing that cannot be seen with an optical microscope. Bacteria are microbes that have been observed only with the aid of a microscope, They are of two major types, Gram-positive and Gram-negative. The colour of the bacterial cell wall in the Gram stain test helps us to differentiate between them because Gram-positive bacteria retain violet dye after being stained with crystal violet. In contrast, the Gram-negative bacteria do not keep this violet dye in the same test.

Microbes and Human Welfare Class 12 Notes

Class 12 Microbes and Human Welfare notes are given on this blog. These notes will be very useful for all class 12 students who are studying Microbes and Human Welfare in their CBSE board or any other board across India and abroad. 


In class, we learned about the role of microbes in human welfare. The first thing we discussed was the gut microbiome. Microbes are mostly bacteria that live in our guts and play an important role in breaking down food. As a result, they help regulate our immune system, maintain our body weight, and help us digest food.

They also assist us with absorbing nutrients from our food. There are 100 trillion microbes in your intestines alone. Without them, you would not be able to live.

What are the 4 types of microorganisms?

There are four types of microorganisms: bacteria, archaea, protists, and fungi.

  1. Bacteria:  Bacteria are a type of microorganism that can exist as either prokaryotes or eukaryotes. Prokaryotes are bacteria without a nucleus, while eukaryotes have a nucleus. There is a third category of organisms called archaea which are similar to bacteria but have different features in their DNA. Bacteria live on the surface of humans, animals, plants and nearly everywhere else.
  2. Archaea: Archaea is a domain of single-celled organisms. Archaea are prokaryotes, which means they lack a membrane-bound nucleus or other organelles. They are able to live in extreme environments that are not available to many other types of organisms. There are two major types of archaea, the Euryarchaeota and Crenarchaeota.
  3. Protists: Protists are a large group of unicellular eukaryotes that includes animals, plants, and fungi. There are a lot of different types of protists but they all have one thing in common: they are single-celled organisms. One type of protist is the amoeba which lives in freshwater ponds.
  4. Fungi: Fungi are eukaryotic organisms that can be unicellular, like yeasts, or multicellular, like mushrooms. They come in many shapes, sizes, colours and textures. Fungi are classified as heterotrophic because they grow on organic materials.

There are three main types of fungi:

  1. Ascomycota: These fungi produce spores inside specialized cells called ascospores. An example of an Ascomycota is the black bread mould.
  2. Basidiomycetes: Basidiomycetes usually form mushroom-like fruiting bodies at the end of a stem or stalk called a mycelium. Some examples include oyster mushrooms and portobello mushrooms.
  3. Deuteromycota: Deuteromycota, also known as imperfect fungi. These fungi lack typical cell walls that contain and protect their cells. Instead, deuteromycete hyphae (threads) may just coil around each other without any surrounding layer protecting them. Examples of Deuteromycota are Candida albicans and Coccidioides immitis.

Role of microorganisms in the environment

It is a very important Microbes and Human Welfare Class 12 Notes. In the environment, microorganisms can be found in places such as soil, water, and air.

They play an important role in many functions of the environment including nutrient cycling, decomposition, disease prevention, waste disposal, food production, and bioremediation.

For example, a bacterium named Pseudomonas aeruginosa is able to detoxify heavy metals such as lead and mercury that can be harmful to both plants and animals. 

Another example of how microbes help humans would be how they help produce our food. The bacteria Lactobacillus fermentum produces lactic acid which makes cheese soft and smooth when it’s aged for more than six months. These bacteria also produce carbon dioxide, acetic acid, lactic acid, propanoic acid, and butyric acid- all important byproducts for making cheese.

Also Check:-
Human Reproduction Class 12 Notes
Biotechnology: Principles and Processes Class 12 Notes
Organisms and Populations Class 12 Notes
Biodiversity and Conservation Class 12 Notes

Impact of microorganisms on human health

The human body is home to trillions of microorganisms, many of which are either good for the body or neutral. There are also those that cause illness in humans. These microbes can be found everywhere on the surface of the body, such as on the skin or in the mouth. They often live in symbiosis with their hosts, but under certain circumstances, they can cause disease. Two key systems that have been linked to our microbial population are our digestive system and immune system.

Our gut contains a complex ecosystem of microorganisms from the moment we are born. Many different factors affect this microbiome including how much stress we experience, what types of food we eat, or if we take antibiotics. Changes in these factors can lead to changes in bacterial populations within the gut. Antibiotics destroy bacteria indiscriminately and disrupt this delicate balance so should not be used unless absolutely necessary.

Use of microorganisms in industries

Use of microorganisms is important Microbes and Human Welfare Class 12 Notes. The use of microorganisms in industries is a very common occurrence. They are used to produce cheese, tofu, bread, beer, yogurt, vinegar, soy sauce, chocolate and many other products we rely on.

The use of microbes in these industries can be seen as beneficial because it can lead to the production of food items that are healthier for humans to consume. For example, yogurt is an excellent probiotic food which means it has beneficial bacteria that aid digestion.

Also, some beers such as Stella Artois and Guinness contain live yeast cultures that have been consumed by billions of people for centuries with no adverse effects. In contrast, not all instances of microbial use in industry are so clear-cut or well-researched.

Use of microorganisms in enzymes and chemicals

Enzymes are proteins that increase the rate of chemical reactions in living organisms. All cells contain enzymes, but there are different types that have special functions depending on where they are found. For example, some enzymes break down food molecules so that nutrients can be absorbed by the body.

Other enzymes help build proteins. One type of enzyme, called lysozyme, breaks down the cell wall of bacteria or other microbes that cause disease. Chymotrypsin is another type of enzyme. It cuts up proteins into smaller pieces. Amylase, which helps digest carbohydrates such as starch and sucrose, is one more enzyme we will mention here.


In conclusion, the human microbiome is an important and fascinating area of study. It has been shown that a person’s microbiome can be altered by what they eat, where they live, and who they spend time with. As we learn more about the microbiome, it will have implications for our understanding of health and disease.

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