Microbes, or microorganisms, are tiny living organisms that can only be seen under a
microscope. They include bacteria, fungi, protozoa, algae, and viruses. Even though
we can’t see them with our eyes, they are all around us—on our skin, in the air, in the
water, and even inside our bodies. These invisible helpers have been on Earth long
before humans and are essential for life to continue.
While we often think of microbes as disease-causing germs, many of them are
beneficial and play a vital role in supporting life. In fact, without microbes, many of
our everyday processes—like making curd, treating sewage, or even producing
medicine—would not be possible. Microbes are the unsung heroes of life on Earth,
silently working to keep everything balanced.
Importance of Microbes in Daily Life
Microbes influence many parts of our lives. They help make our food, clean up
waste, and even help plants grow. Here’s how:
In food: Microbes help make curd, bread, and alcoholic drinks.
In medicine, they are used to make antibiotics and vaccines.
In agriculture, Microbes improve soil fertility and control pests.
In the environment, they treat sewage and help reduce pollution.
Because of their usefulness, microbes are widely used in industries, homes,
agriculture, and environmental science. They offer sustainable solutions that are
eco-friendly and effective.
Microbes in Household Food Processing
Microbes in Curd Formation
One of the most common uses of microbes at home is in making curd from milk. This
simple process involves the help of a friendly bacterium called Lactobacillus. This
bacterium is present in a small amount of curd that we use to set fresh curd.
Here’s how it works:
Lactobacillus converts lactose (milk sugar) into lactic acid.
The acid causes the milk to thicken and form curd.
The lactic acid also gives curd its slightly sour taste.
This process is not just about taste , it also makes milk easier to digest. The bacteria
in curd help improve gut health by increasing the number of good bacteria in the
intestine.
This microbial activity also increases the Vitamin B12 content in the curd. It’s a great
example of how a microbe can make food healthier and more nutritious.
Fermentation in Bread and Dosa
Ever wondered how bread becomes fluffy or how dosa batter rises overnight? It’s all
thanks to a type of fungus called Saccharomyces cerevisiae, also known as baker’s
yeast.
In bread making, yeast ferments the sugars in flour, releasing carbon dioxide.
This gas gets trapped in the dough, making it rise and become soft.
When baked, the bubbles expand, giving the bread its spongy texture.
Similarly, dosa and idli batters are fermented with the help of naturally occurring
microbes like Leuconostoc and Streptococcus. These microbes produce acids and
gases during fermentation that make the batter sour and fluffy.
Fermentation by microbes not only improves texture and flavour but also boosts
nutritional value. For instance, the fermentation process increases the levels of B-
complex vitamins in the food.
Pickles and Vinegar: Preserving with Microbes
Pickling is another traditional household method where microbes play a role. Certain
bacteria like Lactobacillus help in fermenting vegetables, which increases their shelf
life and adds a tangy flavour. These fermented pickles are full of probiotics, which
promote digestive health.
Vinegar, on the other hand, is produced using Acetobacter bacteria. These microbes
convert ethanol into acetic acid, giving vinegar its sour taste. Vinegar is widely used
as a preservative, in salad dressings, and in cooking.
So, without microbes, many of our favourite foods would either not exist or wouldn’t
be nearly as tasty or healthy!
Microbes in Industrial Production
Antibiotics and Vaccines
The first antibiotic, penicillin, was discovered by Alexander Fleming from the
fungus Penicillium notatum. It became a life-saving drug during World War II
and is still used today to treat bacterial infections.
Other antibiotics like streptomycin, erythromycin, and tetracycline are also
produced by microbes.
Vaccines are another gift of microbes. Some vaccines are made using attenuated
(weakened) or inactivated microbes that stimulate the body to build immunity
without causing disease.
Microbes used in vaccine production:
Salmonella typhi → Typhoid vaccine
Mycobacterium tuberculosis (weakened) → BCG vaccine for TB
Industrial setups use fermenters or bioreactors to grow microbes in large quantities
for producing antibiotics and vaccines. These medicines save millions of lives every
year.
Production of Alcohol and Beverages
Microbes are central to the alcohol industry. The same yeast that helps in
baking—Saccharomyces cerevisiae—is also used in alcohol production.
In beer making, yeast ferments sugars in barley or other grains to produce
ethanol and carbon dioxide.
For wine, fermentation happens in fruit juices, usually grape juice.
For rum and whiskey, molasses (a by-product of sugarcane) is fermented.
Alcoholic beverages are classified based on the raw material and fermentation
method. The whole process is natural, relying entirely on microbial action.
Enzymes and Organic Acids
Microbes also produce important industrial enzymes:
Streptococcus → Streptokinase (used to dissolve blood clots)
Aspergillus niger → Pectinase (used in fruit juice clarification)
Trichoderma reesei → Cellulase (used in denim finishing)
Organic acids like citric acid (from Aspergillus niger), acetic acid (from Acetobacter),
and lactic acid (from Lactobacillus) are produced by microbial fermentation and used
in foods, medicines, and cosmetics.
Microbes in Sewage Treatment
Primary and Secondary Treatment
Sewage treatment is a major application of microbes in environmental management.
Raw sewage contains a mixture of human waste, food particles, soaps, and other
contaminants. Treating this waste before releasing it into water bodies is essential to
prevent pollution and disease.
Primary treatment is the physical removal of solid particles. In this step:
Sewage is passed through screens to remove large objects.
Grit chambers remove sand and small stones.
Sedimentation tanks allow heavier particles to settle down, forming primary
sludge.
But primary treatment only removes about 30–40% of waste. The rest of the organic
matter is treated in the secondary or biological treatment stage. This is where
microbes come into play.
In secondary treatment:
The sewage is pumped into large aeration tanks.
Air is bubbled through the tanks to promote the growth of aerobic bacteria.
These microbes digest organic matter and clump into flocs.
The resulting sludge is then sent to settling tanks.
This microbial activity reduces Biological Oxygen Demand (BOD)—a key measure of
water pollution. A lower BOD indicates cleaner water. The leftover sludge can be
further processed for energy generation or used as fertilizer.
Role of Microbes in Bioreactors
Modern sewage treatment plants use bioreactors to grow specific bacterial cultures
that speed up the breakdown of organic matter. These reactors are designed to:
Maintain optimal conditions for microbial growth.
Maximise oxygen supply.
Promote the formation of flocs and biofilms.
Key microbes used include species of Pseudomonas, Nitrosomonas, and
Nitrobacter. These bacteria help remove nitrogenous wastes and convert harmful
substances into harmless byproducts.
By treating sewage biologically, we not only clean wastewater but also avoid using
harmful chemicals, making the process eco-friendly.
Advantages of Microbial Sewage Treatment
Using microbes for sewage treatment has multiple benefits:
Environmentally safe: No chemical residues.
Cost-effective: Reduces the need for expensive chemicals.
Sustainable: Sludge can be recycled as biogas or fertilizer.
Efficient: Removes harmful bacteria and reduces disease risk.
In many developing countries, untreated sewage is a big problem. Promoting
microbial treatment can play a key role in improving public health and conserving
water bodies.
Microbes in Energy Generation
Biogas Production by Methanogens
Biogas is a clean and renewable source of energy produced by microbial activity.
The main microbes involved are methanogenic bacteria, like Methanobacterium.
Here’s how it works:
Organic waste like cow dung or vegetable scraps is placed in an anaerobic
digester (a sealed tank).
In the absence of oxygen, methanogens break down the organic matter.
The main products are methane (CH₄), carbon dioxide (CO₂), and
hydrogen (H₂).
The methane-rich gas can be used for:
Cooking
Lighting
Powering generators
The leftover slurry is rich in nutrients and can be used as manure. Biogas plants are
especially useful in rural areas, offering a clean and sustainable energy source while
managing organic waste.
Q: Which gas is majorly present in biogas?
o A: Methane
Biofuels and Microbial Fuel Cells
Apart from biogas, microbes are being used to produce biofuels like ethanol and
biodiesel. For example:
Saccharomyces cerevisiae ferments sugarcane juice or molasses into
ethanol.
Certain algae and bacteria can be engineered to produce biodiesel from
waste oils.
Microbial fuel cells (MFCs) are an exciting new technology. In MFCs:
Microbes oxidize organic matter and transfer electrons to an electrode.
This creates a flow of electricity.
Though still in research stages, microbial fuel cells could revolutionize how we think
about renewable energy. Imagine powering homes and gadgets using waste and
bacteria—science fiction turning into science fact!
Microbes as Biocontrol Agents
Pest Control with Microbial Insecticides
Farmers often rely on chemicals to kill pests, but these pesticides can harm the
environment, wildlife, and even humans. A better solution is using biocontrol
agents, which are microbes that naturally kill or suppress pests.
For example:
Trichoderma is a fungus used to control plant pathogens.
Bacillus thuringiensis (Bt) produces a toxin that kills insect larvae.
Microbial pesticides are safe, specific to pests, and biodegradable. They don’t harm
beneficial insects like bees and butterflies.
NEET Question:
Q: Bt toxin is obtained from?
o A: Bacillus thuringiensis
Microbial biocontrol is widely used in organic farming and is gaining popularity as
consumers demand pesticide-free food.
Examples like Bacillus thuringiensis (Bt)
Bt is a superstar in microbial pest control. The bacterium produces cry proteins,
which become toxic in the alkaline environment of insect guts. These proteins:
Bind to the gut lining of the insect.
Create pores, causing the insect to die of starvation and infection.
Bt is sprayed on crops or engineered into them (like Bt cotton) to provide built-in pest
resistance.
Benefits:
Reduces chemical pesticide use.
Increases crop yield.
Environmentally safe.
Microbes as Biofertilizers
Nitrogen Fixing Bacteria and Cyanobacteria
Soil health is key to good farming, and microbes help improve it naturally.
Nitrogen-fixing bacteria like Rhizobium live in root nodules of legume plants and
convert atmospheric nitrogen into forms that plants can use. Other nitrogen-fixers
include:
Azospirillum
Azotobacter
Cyanobacteria like Anabaena and Nostoc also fix nitrogen and improve soil fertility.
They are especially useful in paddy fields.
Using these microbes as biofertilizers reduces the need for chemical fertilizers,
which can be harmful to soil and water.
Mycorrhizae and Soil Health
Mycorrhizae are fungi that form symbiotic associations with plant roots. They help:
Increase water and mineral absorption.
Protect plants from pathogens.
Improve soil structure.
For example, Glomus species of mycorrhiza are widely used in agriculture.
Biofertilizers offer a sustainable and eco-friendly way to enhance crop production
and maintain soil quality.
Advantages and Limitations of Using Microbes
Eco-Friendly Nature
The most significant advantage of using microbes in human welfare is their eco-
friendly nature. Unlike synthetic chemicals or heavy machinery, microbes work
silently and efficiently without harming the environment.
Let’s break it down:
In agriculture, microbes reduce the need for chemical fertilizers and
pesticides, keeping soil fertile and water bodies unpolluted.
In waste management, they decompose organic matter, making waste useful
again as compost or biogas.
In industry, microbes help manufacture products at room temperature and
normal pressure, reducing energy consumption.
In medicine, antibiotics and vaccines from microbes save lives without the
toxic side effects of some synthetic drugs.
Because microbes are biodegradable, they don’t leave behind harmful residues.
They’re part of nature’s recycling system, helping maintain balance in ecosystems.
Additionally, microbial methods are often cheaper and easier to implement in rural or
resource-poor areas, making them accessible to all.
Risks and Precautions
Despite their usefulness, microbes must be handled with care. Some risks include:
Contamination: In food and industrial production, unwanted microbial growth
can spoil products or introduce harmful pathogens.
Health risks: Not all microbes are friendly—some can cause diseases if
accidentally introduced into the wrong environment.
Overuse or misuse: Relying too heavily on a single type of microbe (e.g., Bt
in agriculture) may lead to resistance in pests or ecological imbalance.
To prevent these issues:
Proper hygiene and sterilization techniques should be used.
Waste must be handled carefully to avoid biohazards.
Research and regulation are needed to monitor the release of genetically
modified microbes into the environment.
In short, while microbes are powerful tools, they must be used wisely and
responsibly.
NEET Previous Year Questions (2015–2024) on Microbes
Commonly Asked Concepts
Every year, NEET includes questions related to microbes and their roles in different
fields. Some of the most common concepts include:
Microbes in curd and alcohol production.
Methanogens in biogas plants.
Antibiotic-producing microbes.
Bt toxin and its mode of action.
Nitrogen-fixing bacteria in biofertilizers.
These topics are not only directly mentioned in NCERT but are also very
straightforward to understand and memorize. Scoring from these topics is easy if
students focus on keywords and microbial names.
Sample PYQs with Answers
Here are some actual NEET previous year questions:
- NEET 2021
o Which one of the following microbes is used for production of citric
acid?
o A. Aspergillus niger
o B. Acetobacter aceti
o C. Clostridium butylicum
o D. Lactobacillus
o Answer: A - NEET 2020
o Which of the following is used as a biofertilizer in paddy fields?
o A. Azotobacter
o B. Anabaena
o C. Rhizobium
o D. Mycorrhiza
o Answer: B - NEET 2019
o Bt toxin is produced by which of the following bacteria?
o A. Bacillus subtilis
o B. Bacillus thuringiensis
o C. Bacillus anthracis
o D. Bacillus cereus
o Answer: B - NEET 2018
o Methanogens are not found in:
o A. Rumen of cattle
o B. Human intestine
o C. Anaerobic sludge
o D. Hot springs
o Answer: D
- NEET 2017
o Which of the following is used to increase soil fertility?
o A. Lactobacillus
o B. Azospirillum
o C. Saccharomyces
o D. Penicillium
o Answer: B
Conclusion
Microbes are nature’s invisible magicians. From the food on our plates to the fuel in
our kitchens, from medicine to agriculture and even cleaning up waste—microbes do
it all. They silently support life on Earth, making them vital for human welfare.
Whether you’re preparing for NEET or simply curious about biology, understanding
the role of microbes opens your eyes to a whole new world. They’re not just tiny ,
they’re mighty.
As we move toward sustainable development and eco-friendly living, the importance
of microbes will only grow. Learning about them isn’t just about exams it’s about the
future.
FAQs
- What are microbes?
Microbes, or microorganisms, are very small living organisms like bacteria, fungi,
viruses, protozoa, and algae. Most are invisible to the naked eye but play huge roles
in our lives—from making food to cleaning waste and producing medicine. - How do microbes help in curd formation?
Lactobacillus bacteria convert lactose (milk sugar) into lactic acid, which curdles the
milk and forms curd. This process improves digestion and enhances the nutritional
value of milk.
- What is the role of bacteria in sewage treatment?
In sewage treatment, bacteria help break down organic waste in the absence of
chemicals. They reduce pollutants and harmful microbes in wastewater, making it
safe for release into rivers or for reuse. - Are microbes harmful or helpful?
Most microbes are helpful and essential to life. They aid in digestion, make
medicines, clean up waste, and grow food. However, a few can cause diseases if
they enter the body in the wrong way. - Why are microbes important in NEET Biology?
Microbes are frequently asked in NEET due to their importance in food production,
health, environment, and industry. Understanding their types and uses helps
students score better and also appreciate biology in real life.
