Introduction of Microbes in Human welfare
Microbes or microorganisms form a big component of the biological systems of the world. They are ubiquitous, present everywhere – within the soil, around us, in water, the air we breathe, and both in and on our bodies. Animals and plants also contain microbes or microorganisms. They are so tiny, microscopic in nature, varying in shape and size. They can only be seen through the microscope. The different types of microbes are:
Algae
Bacteria
Fungi
Protozoa
Virus
Microbes in Human Welfare
There are several useful microorganisms that are beneficial to humans in various ways apart from harmful and infectious disease-causing pathogens. Some of the foremost important contributions of microbes to human welfare are discussed below.
In Household Products
Fermentation of milk to prepare yoghurt.
Milk cuddling to prepare curd, cheese, and paneer.
Fermentation of dough, which is used for making-idli, and dosa.
The dough that is used to prepare bread is fermented using Saccharomyces cerevisiae which is also known as baker's yeast.
‘Toddy ‘ a traditional south Indian drink is made by fermenting sap from palms.
Fish, soybean and bamboo shoots are fermented with the help of microbes to produce food.
A type of cheese - Swiss cheese has huge holes in its texture. These holes are produced by a large amount of CO2. This CO2 is produced during the fermentation process because of the bacterium used - Propionibacterium shamanic.
Another type of cheese called the Roquefort cheese is ripened by growing specific fungi on them. This gives the cheese a particular flavour.
In Industrial Products
Production of beverages like wine, beer, whiskey, brandy or rum.
Production of antibiotics like Penicillin and other chemical substances to kill or retard the expansion of disease-causing microbes.
Few Chemicals, Enzymes and other Bioactive Molecules also are produced by these microbes for various human uses.
Fermented Beverages
To produce microbes on a large scale for industrial purposes a vessel named fermentor is used.
The brewer’s yeast (Saccharomyces cerevisiae) is used to produce ethanol. Here the yeast ferments malted cereals and fruit juices.
The alcohol produced using distillation is wine, whereas the ones that are produced without distillation are whisky, brandy and rum.
Antibiotics
Antibiotic means “against life” in Greek. These are substances that can kill or destroy the growth of other microbes.
Penicillin was the first antibiotic discovered from the Staphylococci bacteria by Alexander Fleming.
Penicillin was named after the moulds Penicillium notatum. It was used to treat soldiers in the USA during WW2.
Antibiotics today have been developed to treat many deadly diseases like whooping cough, leprosy, diphtheria, etc.
Chemicals, Enzymes and Other Bioactive Molecules
A fungus named Aspergillus niger produces citric acid.
A bacterium named Acetobacter aceti produces acetic acid.
Another bacterium named Clostridium bretylium produces butyric acid and a bacterium named Lactobacillus produces lactic acid.
The oily laundry stains are removed using the lipases which are present in the detergent formulations.
The bottled juices in shops are clarified using pectinases and proteases.
Streptococcus which produces the streptokinase is used as a clot-buster in medical treatments.
Trichoderma polysporum produces a bioactive molecule named cyclosporin which helps as an immunosuppressive in organ transplant surgery.
A yeast named Monascus purpureus produces statins that help lower blood cholesterol levels.
In Sewage Treatment
Sewage is treated in sewage treatment plans (STPs) before disposing of it so as to make it less polluting which is naturally carried out by heterotrophic microbes present in the sewage. The treatment is administered in two stages – primary treatment, secondary treatment or biological treatment.
Primary treatment
During primary treatment, physical particles are removed from the sewage using the filtration and sedimentation method.
Initially, the floating debris is removed by filtration.
After filtration, the soil and rocks in the debris are removed by the process of sedimentation.
Solids from the primary sludge and the supernatant from the effluent.
Secondary Treatment
It is also known as biological treatment.
The effluent from primary treatment is taken forward for the secondary treatment.
The large aeration tanks here perform the mechanical work and pump air into the tank so as to agitate the effluents.
This process accelerates the growth of large numbers of aerobic bacteria eventually leading to flocs.
Flocs are the mesh-like structures formed during the treatment of sewage.
These processes minimize the demand for biochemical oxygen of the effluent significantly. BOD is the amount of oxygen that might be consumed if all the organic matter in one litre of water were oxidized by the bacteria. The sewage water is treated to reduce the effect of BOD as the BOD gauges the rate of uptake of oxygen by microbes in a water sample. Therefore, BOD may be a measure of the organic matter present in water. The more the demand for biochemical oxygen, the more is its polluting potential.
The significant decrease in the BOD forces the effluents to pass and settle down in the settling tanks, where they are allowed to sediment.
This active sludge is then pumped back to aeration tanks and then to larger tanks for the process of anaerobic sludge digestion.
Anaerobically here the other bacteria and fungus digest the sludge.
In Biogas Production
Biogas is used as a fuel and is produced by microbial activity. It is a mixture of gasses containing high concentrations of methane.
Methanobacterium, commonly found in anaerobic sludge, is used to facilitate sewage treatment.
They are also found in the rumen of ruminants.
Thus they help in the process of digestion of cellulose and play a vital role in the nutrition of the cattle.
The excreta of cattle, also known as Gobar is rich in bacteria and therefore is used for the generation of biogas commonly termed as fertilizer.
As Biocontrol Agents
The utilization of biological methods to regulate plants pests and diseases is mentioned as biocontrol which has been achieved through chemicals – pesticides and insecticides.
The use of biocontrol measures will reduce the dependence on toxic chemicals and pesticides to a greater extent.
Biological farming enhances the life forms like the inhabiting of the sector, pests and predators, life cycles, feeding patterns that help in developing suitable means of biocontrol.
Bacillus thuringiensis, available as dry spores, sprayed on vulnerable plants are some of the examples of microbial biocontrol agents.
Genetic engineering developments have enabled scientists to release B. thuringiensis toxins genes into the plant body thereby making them resistant to attacks by insect pests. For example – Bt-cotton.
Most of the baculoviruses used as biological control agents are within the genus Nucleopolyhedrovirus.
Microbes are also used as biofertilizers.
FAQs on Microbes in Human Welfare
1. What is the role of microbes in producing common household food items?
Microbes are essential for creating many household foods through fermentation. For example:
- Curd: Lactic Acid Bacteria (LAB), like Lactobacillus, convert milk lactose into lactic acid, which coagulates and partially digests milk proteins to form curd.
- Dough: Baker’s yeast, Saccharomyces cerevisiae, ferments sugars in dough, producing carbon dioxide (CO₂) that causes it to rise, making bread, idli, and dosa spongy.
- Cheese: Different microbes give various cheeses their unique textures and flavours. For instance, specific bacteria and fungi are used to ripen cheese.
- Toddy: This traditional South Indian drink is made by fermenting sap from palms using naturally occurring yeast.
2. How are microbes used on an industrial scale to produce beverages and antibiotics?
On an industrial scale, microbes are grown in large vessels called fermenters to produce valuable products.
- Beverages: Brewer’s yeast (Saccharomyces cerevisiae) is used to ferment malted cereals and fruit juices to produce ethanol for beverages like beer, wine, whiskey, and rum.
- Antibiotics: These are chemical substances produced by microbes that can kill or inhibit other disease-causing microbes. The first antibiotic, Penicillin, was discovered from the mould Penicillium notatum and is used to treat bacterial infections.
3. What is the importance of microbes in sewage treatment plants (STPs)?
Microbes play a crucial role in making municipal wastewater (sewage) less polluting before it is discharged into natural water bodies. In Sewage Treatment Plants (STPs), heterotrophic microbes naturally present in sewage are used to decompose the organic matter. This biological treatment significantly reduces the organic load and pathogens in the water, making it safer for the environment.
4. What is the key difference between primary and secondary treatment in an STP, and what is the significance of Biochemical Oxygen Demand (BOD)?
The key difference lies in their method and purpose:
- Primary Treatment is a physical process that removes large and small particles from sewage through filtration and sedimentation. It separates floating debris and grit.
- Secondary Treatment (or biological treatment) is a microbial process. The primary effluent is passed into large aeration tanks where aerobic microbes grow into masses called flocs. These microbes consume the organic matter present in the effluent.
The significance of Biochemical Oxygen Demand (BOD) is that it measures the amount of oxygen required by aerobic bacteria to break down the organic waste in a water sample. A high BOD indicates high pollution. The main goal of secondary treatment is to drastically reduce the BOD of the sewage.
5. What are biocontrol agents and give an example of a microbial one?
Biocontrol agents are living organisms used to control pests like insects, weeds, and pathogens, reducing the reliance on chemical pesticides. A prime example of a microbial biocontrol agent is the bacterium Bacillus thuringiensis (Bt). It is available as dried spores which, when ingested by insect larvae, release a toxin in their gut that kills them. This microbe is highly specific and does not harm other insects, making it an excellent component of Integrated Pest Management (IPM) programs.
6. How do microbes act as biofertilizers to enrich soil quality?
Biofertilizers are living organisms that enrich the nutrient quality of the soil, mainly by enhancing the availability of nitrogen and phosphorus. Microbes achieve this through several mechanisms:
- Nitrogen Fixation: Bacteria like Rhizobium form symbiotic relationships with the roots of leguminous plants to fix atmospheric nitrogen. Others like Azospirillum and Azotobacter can fix nitrogen while living freely in the soil.
- Phosphorus Solubilisation: Some fungi, like those forming Mycorrhiza, create a symbiotic association with plant roots, helping them absorb phosphorus from the soil.
- Organic Matter Enrichment: Cyanobacteria like Anabaena and Nostoc can fix atmospheric nitrogen and add organic matter to the soil, improving its fertility, especially in paddy fields.
7. Why are methanogens essential for both biogas production and the digestive process in cattle?
Methanogens are a group of anaerobic bacteria that produce methane as a metabolic byproduct. Their importance in both contexts stems from their ability to break down cellulosic material.
- In Biogas Production: In a biogas plant, methanogens anaerobically digest the cellulose present in cow dung (gobar) and other organic waste, producing a mixture of gases, primarily methane (CH₄), which is a combustible fuel.
- In Cattle Digestion: Methanogens are found in the rumen, a part of the cattle's stomach. Here, they help break down the large amounts of cellulose present in the grass and fodder that cattle eat, playing a vital role in their nutrition.
Essentially, they perform the same function of anaerobic digestion in two different, but equally important, environments.
8. What is the difference in the microbial production of antibiotics and bioactive molecules like statins?
While both are valuable products derived from microbes, their functions and sources differ. Antibiotics, such as Penicillin from Penicillium notatum, are specifically used to kill or inhibit the growth of harmful, disease-causing microbes. In contrast, bioactive molecules have specific physiological effects on the human body. For example:
- Statins, produced by the yeast Monascus purpureus, are used to lower blood cholesterol levels by competitively inhibiting the enzyme responsible for cholesterol synthesis.
- Cyclosporin A, produced by the fungus Trichoderma polysporum, acts as an immunosuppressive agent, crucial for preventing organ rejection in transplant patients.
9. Are all microbes harmful pathogens? Explain with examples of their benefits from the Class 12 syllabus.
No, this is a common misconception. While some microbes are pathogens that cause diseases, the vast majority are harmless and many are vital for human welfare and ecological balance. As per the Class 12 syllabus, their benefits are extensive:
- In Households: Lactobacillus helps convert milk to curd.
- In Industry: Yeast helps in baking and brewing, while other microbes produce antibiotics, enzymes, and organic acids.
- In Environment: Microbes are the primary decomposers in sewage treatment, cleaning wastewater.
- In Agriculture: They act as biofertilizers (e.g., Rhizobium) to enrich soil and as biocontrol agents (e.g., Bacillus thuringiensis) to protect crops.
10. How is 'Swiss cheese' different from 'Roquefort cheese' based on the microbes used for their ripening?
The distinct characteristics of different cheeses are a direct result of the specific microbes used during their production:
- Swiss Cheese is known for its large holes. These are formed due to the production of a large amount of carbon dioxide (CO₂) by a bacterium called Propionibacterium shermanii during the ripening process.
- Roquefort Cheese gets its specific strong flavour and veined appearance from being ripened with a fungus, Penicillium roqueforti, which is grown on it.
