Microbes in Human Welfare

Microbes in Human Welfare


Microbes, also known as microorganisms, are tiny living organisms that are too small to be seen with the naked eye. They include various types such as bacteria, viruses, fungi, archaea, and protists. Here are some key points about microbes:


  • Diverse Group: Microbes comprise a vast and diverse group of organisms that inhabit virtually every environment on Earth, including soil, water, air, and even within other organisms.
  • Unicellular: Most microbes are unicellular, meaning they consist of a single cell. However, some may form multicellular structures under certain conditions.
  • Abundant: Microbes are incredibly abundant and exist in large numbers. A single teaspoon of soil may contain billions of microbial cells.
  • Roles in Ecosystems: Microbes play critical roles in ecosystems, where they participate in nutrient cycling, decomposition of organic matter, and symbiotic relationships with other organisms.
  • Pathogens: While many microbes are beneficial or harmless, some can cause diseases in plants, animals, and humans. These pathogenic microbes are responsible for various infectious diseases.
  • Beneficial Functions: Microbes perform numerous beneficial functions, including nitrogen fixation, decomposition of organic matter, production of antibiotics, and fermentation of foods.


Microbes in Household Products


  • Microbes play a crucial role in household products like curd, cheese, and fermented foods such as dosa and idli.
  • Lactic acid bacteria (LAB) like Lactobacillus are used to curdle milk and improve its nutritional quality by increasing vitamin B12.
  • Baker's yeast (Saccharomyces cerevisiae) is used in bread-making for fermentation, leading to the production of CO2 that causes the dough to rise.
  • Traditional drinks like 'toddy' and fermented foods like fish, soybean, and bamboo shoots also utilize microbes for fermentation.
  • Enzymes derived from microbes are used in detergent formulations to remove oily stains from laundry, and in the clarification of bottled fruit juices to make them clearer.
  • Cheese: Different types of cheese are produced through the partial degradation of milk by various microorganisms, such as Propionibacterium sharmanii for Swiss cheese and Penicillium roqueforti for Roquefort cheese.
  • Microbes are also used in the production of bioactive molecules like statins and cyclosporin A, with various applications such as blood-cholesterol lowering and immunosuppression in organ-transplant patients.


Microbes in Industrial Products


Microbes play a crucial role in the production of various industrial products such as beverages, antibiotics, and enzymes. They can be easily grown in laboratories or at industrial scale for research and production of useful products.


Fermented Beverages


  • Fermented beverages like wine, beer, rum, whiskey, brandy, and some non-alcoholic fruit juices are produced in industries following various processes. Microbes are grown in large vessels called fermentors or bioreactors for the production of these beverages.
  • The fermentation process is crucial for the production of fermented beverages. It involves the conversion of sugars into alcohol and carbon dioxide by yeasts or other microorganisms. The type of microorganism used and the conditions of fermentation can significantly affect the taste, aroma, and quality of the final product.
  • Saccharomyces cerevisiae is a widely used microorganism in the production of fermented beverages. It is capable of producing alcohol from sugars only through the anaerobic process. Distillation is used to extract or purify a liquid from a mixture or concentrate it, and is used in the production of whisky, brandy, and rum.
  • In the production of beverages like beer, brandy, rum, wine, whiskey, yeasts are widely used microorganisms. Specifically, the Brewer’s Yeasts, scientifically known as Saccharomyces cerevisiae, are used for fermenting fruit juices and malted cereals to produce ethanol. Post-fermentation, these beverages are distilled to produce both alcoholic and non-alcoholic beverages.





  • Antibiotics, which are chemical substances generated by certain microbes that kill or inhibit the growth of harmful microbes without affecting human cells, are also produced with the help of microbes.
  • The first discovered antibiotic was Penicillin, found by Alexander Fleming in 1928 from the fungus Penicillium notatum. Several other antibiotics, including Streptomycin, are produced by microorganisms to treat various bacterial infectionsIt was later recognised to be an efficient antibiotic by Ernest Chain and Howard Florey.
  • The use of antibiotics has significantly enhanced our ability to cure deadly diseases including leprosy, whooping cough, diphtheria, and plague.


Chemical, Enzymes and Other Bioactive Molecules


Microbes produce a variety of chemicals, including amino acids, organic acids, vitamins, and biofuels. Some examples of these chemicals include:


  1. Lactic acid: Produced by Lactobacillus bacteria through fermentation.
  2. Butanol: Produced by Clostridium butylicum (bacterium) through fermentation.
  3. Ethanol: Produced by Saccharomyces cerevisiae through alcoholic fermentation.
  4. Acetic acid: Produced by Acetobacter aceti (bacterium) through acetic acid fermentation.
  5. Citric acid: Produced by Aspergillus niger (fungus) through citric acid fermentation.




Lipase: Lipases break down fats into glycerol and fatty acids. They are used in detergent formulation to remove oily stains from laundry.

Pectinases and Proteases: They are used to clarify bottled juices.

Streptokinase: They are produced from streptococcus is used as clot buster for removing blood clots from blood vessels of patients.


Bioactive Molecule



Microbes in Sewage Treatment


Sewage is the dirty drain water that contains urine and faeces, which is carried from homes and buildings by underground pipes called sewers. Sewage is treated at sewage treatment plants to reduce pollution by introducing heterotrophic bacteria that are naturally found in sewage. The treatment process involves two main stages: Primary treatment and Secondary treatment.


Primary Treatment 

  • In primary treatment, sewage is stored in a basin where solids (sludge) can settle to the bottom and oil and lighter substances can rise to the top.
  •  These layers are then removed, and the remaining liquid can be sent to secondary treatment. Sewage sludge is treated in a separate process called sludge digestion.


Secondary Treatment 


  • Secondary treatment in sewage treatment is a biological process that involves the use of microorganisms to digest organic waste. This process is also called biological treatment.
  • The primary effluent, which is the partially treated sewage from the primary treatment, is passed into an aeration tank where vigorous growth of aerobic microbes (flocs) takes place. As a result of this, the Biochemical Oxygen Demand (BOD) gets significantly reduced.
  • The effluent is then passed to a settling tank where flocs sediment to produce activated sludge. This sludge is pumped to an anaerobic sludge digester to digest the bacteria and fungi in the sludge.
  • The microorganisms used in secondary treatment are mostly aerobic bacteria that use free oxygen within the water to degrade the pollutants in the wastewater and then convert it into energy that they can use to grow and reproduce. These bacteria require oxygen to be added mechanically to the water for them to function correctly.
  • Secondary treatment is designed to remove dissolved and suspended biological matter, often using microorganisms in a controlled environment. Most secondary treatment systems use aerobic bacteria, which consume the organic components of the sewage (sugar, fat, and so on). 
  • Some systems use fixed film systems, where the bacteria grow on filters, while others use suspended growth systems, where the bacteria are mixed directly into the sewage.




Microbes in Production of Biogas


  • Biogas is a mixture of gases (mainly CH4, CO2, H) produced by certain bacteria, which grow anaerobically on cellulosic material.These bacteria are collectively called methanogens.
  • Microbes play a crucial role in the production of biogas. Methanogens, such as Methanobacterium, are key microbes involved in this process. These bacteria, found in environments like the rumen ( a part of stomach) of cattle, produce methane, carbon dioxide, and hydrogen under anaerobic conditions, leading to the production of biogas commonly called gobber gas.
  • The production of biogas involves a series of stages catalyzed by different microorganisms, including fermentative microbes, acetate-forming microbes, and methane-producing microbes.
  • Methanogens are essential in the final stage of biogas production, where they convert organic matter into methane and carbon dioxide, contributing to the energy-rich composition of biogas. The biogas production process is enzyme-driven and relies on the activity of various ion-specific transporters and enzymes present in these microbial communities.


Bio-Gas Plants


Biogas plants are facilities that provide oxygen-free conditions for anaerobic digestion to occur. They are artificial systems that convert organic matter into biogas, a renewable energy source, through the action of certain bacteria under anaerobic conditions. Biogas is a mixture of gases, primarily methane, carbon dioxide, and hydrogen, which can be used for cooking, lighting, and reducing environmental pollution.


Components of a Biogas Plant - A biogas plant consists of five main components:


  1. Inlet: This is the entry point for the slurry, which is a mixture of organic matter and water.
  2. Fermentation chamber: This is where the biogas is produced by the activity of microorganisms under anaerobic conditions.
  3. Gas storage tank: This is where the biogas is stored for later use.
  4. Outlet: This is the exit point for the used slurry, which can be used as a fertilizer due to its high nutrient content.
  5. Exit pipe: This is the pipe through which the biogas is removed from the plant for use.



The organic matter is fed into the digesters, which are completely submerged in water to provide anaerobic conditions. The microorganisms break down the organic matter and convert it into biogas, which is then supplied to the respective places through the exit pipes. The biogas produced is used for cooking and lighting.


The technology of biogas production was developed in India mainly due to the efforts of Indian Agricultural Research Institute (IARI) and Khadi and Village Industries Commission (KVIC).


Microbes as Biocontrol Agent


  • Microbes are used as biocontrol agents to control pests and diseases in agriculture, forests, natural resources, stored products, and aquatic environments. They act via a range of modes of action, including antibiosis, host colonization, nutrient or niche competition, induced resistance, parasitism, and antagonism. 
  • Biocontrol agents are an integral part of organic farming, where they maintain a balance of useful and harmful agents within the system. Chemical methods used for eradicating pests and parasites can sometimes be ineffective and can harm beneficial organisms. Therefore, biocontrol agents that naturally prey on harmful insects and pests are preferred.
  • Microorganisms such as bacteria, fungi, viruses, and protozoans serve as biocontrol agents by causing diseases in pests, competing with them, or directly killing them. Biotechnology has led to the development of various biocontrol agents.


Examples of microbes as biocontrol agents include:


  1. Bacteria: Bacteria such as Bacillus thuringiensis (Bt) are widely used as biocontrol agents. A solution containing Bt spores can be sprayed on plants to eliminate caterpillars. When ingested, these spores release toxins in the caterpillar's gut, leading to their death. Other bacteria, such as Pseudomonas, Agrobacterium, Arthrobacter, and Rhizobium, can also act as biocontrol agents by producing antimicrobial compounds that inhibit the growth of plant pathogens.
  2. Fungi: Fungi such as Trichoderma and Entomophaga are used as biocontrol agents. Trichoderma can inhibit the growth of plant pathogens by producing enzymes that degrade their cell walls. Entomophaga is a fungus that infects and kills insects, such as green peach aphids.
  3. Viruses: Viruses such as baculoviruses of the genus Nucleopolyhedrovirus are used as biocontrol agents. Baculoviruses infect and kill insects by replicating inside their cells and causing lysis.


Integrated Pest Management 

IPM is an effective and environmentally sensitive approach that offers a wide variety of tools to reduce contact with pests. It helps to reduce the number of pests, reduce the number of pesticide applications, and save money while protecting human health. IPM is used in agriculture, horticulture, forestry, human habitations, and other settings to manage pests while minimizing the use of pesticides and protecting the environment.


Microbes as Biofertilisers


Biofertilizers are substances containing microorganisms that help with soil fertility, making plants grow in a healthy way and increasing the flow of vital nutrients in trees and plants. They can be divided into different types based on the type of microbe used and mode of action, including nitrogen-fixing bacteria, fungi, and cyanobacteria.

The different types of microbes used as biofertilizers include:


  • Rhizobia: These bacteria form symbiotic relationships with leguminous plants, converting atmospheric nitrogen into ammonia that the plants can use. This process, known as nitrogen fixation, increases the nitrogen content of the soil and promotes plant growth.
  • Azotobacter: These free-living nitrogen-fixing bacteria are found in the rhizosphere of various crops and help fix atmospheric nitrogen, improving soil fertility and promoting plant growth.
  • Azospirillum: These free-living nitrogen-fixing bacteria are also found in the rhizosphere of various crops and help promote plant growth by producing plant growth hormones.


  • Mycorrhiza: Fungi forming symbiotic associations with plant roots, enhancing nutrient uptake.


  • Blue-green algae (BGA): These cyanobacteria can fix atmospheric nitrogen and are often used in rice cultivation to improve soil fertility and promote plant growth.
  • Azolla: This aquatic fern forms a symbiotic relationship with nitrogen-fixing cyanobacteria, making it an excellent biofertilizer for rice cultivation.

These microbes are used as biofertilizers due to their ability to enhance soil fertility, promote plant growth, and reduce the need for chemical fertilizers, making them an eco-friendly and cost-effective alternative for sustainable agriculture.