CBSE Class 12 Biology Microbes In Human Welfare Notes Set B

Download CBSE Class 12 Biology Microbes In Human Welfare Notes Set B in PDF format. All Revision notes for Class 12 Biology have been designed as per the latest syllabus and updated chapters given in your textbook for Biology in Standard 12. Our teachers have designed these concept notes for the benefit of Grade 12 students. You should use these chapter wise notes for revision on daily basis. These study notes can also be used for learning each chapter and its important and difficult topics or revision just before your exams to help you get better scores in upcoming examinations, You can also use Printable notes for Class 12 Biology for faster revision of difficult topics and get higher rank. After reading these notes also refer to MCQ questions for Class 12 Biology given our website

Microbes In Human Welfare Class 12 Biology Revision Notes

Class 12 Biology students should refer to the following concepts and notes for Microbes In Human Welfare in standard 12. These exam notes for Grade 12 Biology will be very useful for upcoming class tests and examinations and help you to score good marks

Microbes In Human Welfare Notes Class 12 Biology

Chapter – 10:

Microbes in Human Welfare

Microbes are present everywhere.
E.g. Thermal vents of geyser (Temp. above 1000 C) Deep in soil. Under snow.

Diverse. Protozoa, Bacteria, Fungi, Virus, Viroids, Prions (Proteinaceous infectious agents)
Useful : Antibiotics.
Harmful: cause diseases.
In Household Products: Everyday : Lactobacillus (LAB) Lactic acid Bacteria – form curd from milk. Increase Vit . 

Check disease causing microbes in our stomach. Fermentation of dough for dosa, idli (CO2 produced) Making bread –Baker’s yeast.Saccharomyces cerevisiae.

Toddy made from sap of palm.
Cheese making (eg.Swiss cheesse by Propionibacterium sharmanii, Roquefort cheese by fungi.)

In Industrial Products :
Beverages and antibiotics.
Fermentors : Large vessels for growing microbes.

Fermented Beverages :
Beverages like wine, bear, whisky, Brandy, Rum (Saccharomyces cerevisiae)
Malted cereals and fruit juices used to produce ethanol, wine and beer produced without distillation. Whisky, brandy, rum produced after distillation.

Antibiotics : (Against life)
Penicillin produced by Alexander Fleming from Penicillium notatum while working with Staphylococci Earnest Chain and Howard Plorey awarded Nobel Prize in 1945 for establishing Penicillin as an effective antibiotic.
Uses : Treat diseases like plague, whooping cough, diphtheria, leprosy.
Chemicals: Enymes and other Bioactivities Molecules:

Aspergillus nigerfor production of Citric Acid.
Acetobacter aceti for production of Acetic Acid.
Clostridium butylicum for production of Butynic Acid.
Lactobacillus for production of Lactic acid. Lipases used in detergents to remove oil strains from Laundry.
Pectinases and Proteases to clarify bottled jucies.

Streptokinase (from Streptococcus) as clot buster in patients with myocardial infraction (heart attack).
Cyclosporin A– an immunosuppresant used in organ transplant patients (produced by Trichoderma polysporum)
Statins produced by yeast Monascu spurpureus used as blood, cholesterol lowering agent.

Microbes in sewage Treatment:
Why treatment necessary?
Major component of waste water, human excreta.
Waste water sewage.
Cannot be disposed directly into rivers and streams. Where & how?
Before disposal sewage treated in sewage treatment plants (STPs)
Treatment done in two stages.
Primary : Physical removal of particles large and small by filtration and sedimentation.
Solids – primary sludge.
Supernatant – effluent.
Secondary: Primary effluent taken to large aeration tanks.
Agitated mechanically and air pumped into it.
Aerobic microbes form masses with fungal filaments flocs.
Microbes consume organic matter in effluent for growth.
BOD ( Biological oxygen demand) reduced.
Passed into settling tank. 
Bacterial flocs sedimented (activated sludge)
Small part of activated sludge used as inoculums in aeration tank.
Major part pumped into large anaerobic sludge digesters.
Anaerobic bacteria digest bacteria and fungi.
Bacteria produce gases such as menthane, hydrogen sulphide and CO2 – Biogas.
Secondary effluent released into rivers and streams.
No man made technology available till date.
Untreated sewage if released into rivers causes pollution.
Ministry of environment and Forests iniatiated, Ganga Action Plan and Yamuna Action Plan.
CBSE Class 12 Biology - Microbes in Human Welfare notes

Biogas plant:
Concrete tank 10- 15 mts deep, slurry or dung fed.
Floating cover placed above rises as biogas content rises.
Connecting pipe for supply of biogas.
Used for cooking and lighting.
Development by IARI :- Indian Agriculture Research institute & KVIC:-Khadi and village Industries Commission.

Microbes as Biocontrol Agents :
Insecticides and Pesticides toxic, harmful & are pollutants.
Natural predation better method.
No of pests kept in check, not totally eradicated.
Food chains not disturbed
Eg. Ladybird and Dragon flies useful to get rid of aphids and mosquitoes.
Bacillus thuringiensis (Bt) used to control butterfly caterpillar.
Mode of spores operation.
Available is sachets, mixed with water and sprayed on plants.
Eaten by insect larva
Toxin released in gut kills larvae.
Now Bt toxin genes introduced into plants – resistant to insect pests.e.g. Bt cotton.
Fungus Trichoderma now being developed.
Nucleo polyhedrovirus– good for narrow spectrum insecticide applications.

Advantages :-
No negative impacts on plants, mammals, birds, fish or target insects.
For overall IMP (Intergrated pest Management) programme.
For ecologically sensitive areas.

As Biofertilizers:
Chemical fertilizers major pollutant.
Switch to organic farming and use of biofertilizers need of the time.
Main sources of biofertilizers. Bacteria, Fungi & Cyanobacteria.
Eg Rhizobium present in roots of leguminious plants fix atmospheric nitrogen into usable organic form. Azospirillium and Azotobacter – free living bacteria – fix atmospheric Nitrogen.
Symbiotic Associations
Eg.Genus Glomus sp. form mycorrhiza
Fungal symbiont absorbs phosphorus from soil and passes it to plant.

Plants show
 resistance to root – borne pathogens.
Tolerance to salinity and drought
Increase in growth and development.

Cynobacteria– autotrophic – fix atmospheric nitrogen Imp.biofertilizer.
e.g. Anabaena, Nostoc, Oscillatoria.
Blue green algae – increase fertility by adding organic matter.
No. of biofertilizers are commercially available.
For production of biodegradable plastics:
biodegradable plastic, e.g. polyhydroxybutyrate (PHB) is being produced commercially by fermentation with the bacterium Alcaligenes eutrophus.
Production of PHB may be easily achieved in tree plants like populous, where PHB can be extracted from leaves.
Other main drawback of bacterial PHB is its high production cost, making it substantially very expensive than synthetic plastics.

As edible vaccines:
The genes encoding the antigenic proteins of virus and bacteria can be isolated from the pathogens and expressed in plants.
Such transgenic plants or their tissues producing antigens can be eaten for vaccination/immunization (edible vaccines).
The expression of such antigenic proteins in crops like banana and tomato are useful for immunization of humans since banana and tomato fruits can be eaten raw. Example: cholera and hepatitis B vaccine.
Process of sewage treatment in STP
a)Primary treatment(physical )
b)Secondary treatment(biological)
Effluent loaded in large aeration tank, Agitation & rapid growth of aerobic microbes (flocs) ,Consumes organic matter ,reduces BOD, Effluent passed to settling tank, Floc sediments form – activated sludge(A.S.),Poured into sludge digester(small amount of A.S. used as inoculum) Filtration & sedimentation.

Very Short Answer Type Questions

Question. Why do we prefer to call secondary waste water treatment as biological treatment?
Answer : Secondary waste water treatment is called biological treatment because microorganisms are involved in the breakdown of organic matter in this phase of waste water treatment. The primary effluent is passed into large aeration tanks where the organic matter in it is consumed by aerobic microbes which are later themselves digested by anaerobic bacteria and fungi in anaerobic sludge digesters.

Question. Why is distillation required for producing certain alcoholic drinks?
Answer : Depending on the type of the raw material used for fermentation and the type of processing (with or without distillation) different types of alcoholic drinks are obtained. Wine and beer are produced without distillation whereas whiskey, brandy and rum are produced by distillation of the fermented broth. Distillation increases the alcohol content in alcoholic drinks. That’s why for producing certain alcoholic drinks, distillation is required.

Question. Write the most important characteristic that Aspergillus niger, Clostridium butylicum, and Lactobacillus share.
Answer : Their common characteristic is that they produce organic acids as part of their metabolism and are therefore, used for commercial and industrial production of the same. (i) Aspergillus niger (a fungus) for citric acid. (ii) Clostridium butylicum (a bacterium) for butyric acid. (iii) Lactobacillus (a bacterium) for lactic acid.

Question. What for nucleopolyhedro viruses are being used now a-days?
Answer : Several methods of biological control are being used in the pest management to keep the pollution-free environment and yield clean, non-toxic and good quality products for human consumption. Baculoviruses are a group of viruses used as biological control agents that occur naturally and are specific to some insects. Most of the baculoviruses belong to the genus Nucleopolyhedro virus. These viruses are excellent candidates for species-specific, narrow spectrum insecticidal applications. They have been shown to have no negative impacts on plants, mammals, birds fish or even on non-target insects. This is especially desirable when beneficial insects are being conserved to aid in an overall Integrated Pest Management (IPM) Programme or when an ecologically sensitive area is being treated.

Question. How has the discovery of antibiotics helped mankind in the field of medicine?
Answer : Antibiotics produced by microbes are regarded as one of the most significant discoveries of the twentieth century and have greatly contributed towards the welfare of the human society. Anti is a Gk. word that means ‘against’ and bio means ‘life’, together they mean ‘against life’ (in the context of disease causing organisms); whereas with reference to human beings, they are ‘pro life’ and not against. Antibiotics are chemical substances, which are produced by some microbes and can kill or retard the growth of other (disease-causing) microbes. Antibiotics have greatly improved our capacity to treat deadly diseases such as plague, whooping cough (Kali khansi), diphtheria (Gal ghotu) and leprosy (Kusht rog), which had killed millions all over the globe. Today, we can not imagine a world without antibiotics.

Question. Why does ‘Swiss cheese’ have big holes?
Answer : The large holes in ‘Swiss cheese’ are due to production of a large amount of CO2 by a bacterium named Propionibacterium sharmanii.

Question. What are fermentors?
Answer : For large scale production of biotechnological products, e.g., antibiotics, beverages) in industries, microbes are grown in very large vessels called fermentors or bioreactors.

Question. Name a microbe used for statin production. How do statins lower blood cholesterol level?
Answer : Statins are bioactive molecules, produced by the yeast Monascus purpureus. These bioactive molecules have been commercialised as blood-cholesterol lowering agents. It acts by competitively inhibiting the enzyme responsible for synthesis of cholesterol.

Short Answer Type Questions

Question. Why are cyanobacteria considered useful in paddy fields?
Answer : Cyanobacteria like Anabaena, Nostoc, Oscillatoria serve as an important biofertiliser in paddy fields as they fix atmospheric nitrogen and add organic matter to the soil and increase its fertility.

Question. How was penicillin discovered?
Answer : Penicillin was the first antibiotic to be discovered and it was a chance discovery. Sir, Alexander Fleming observed that in unwashed culture plates of Staphylococcus, a mould Penicillium was growing. This mould inhibited the growth of Staphylococcus. Later the antibiotic was isolated from this fungus and named penicillin after the mould Penicillium notatum.

Question. Which bacterium has been used as a clot buster? What is its mode of action?
Answer : The bacterium Streptococcus that produces streptokinase is used as a 'clot buster'. This enzyme has a fibrinolytic action that breaks down the clots formed in the blood vessels of patients who have undergone myocardial infarction. This prevents heart attack in these patients that can otherwise occur because of occlusion by the clots.

Question. What are biofertilisers? Give two examples.
Answer : Biofertilisers are organisms that enrich the nutrient quality of the soil. The main source of biofertilizers are bacteria, fungi and cyanobacteria. e.g., (i) Azospirillum, Rhizobium and Azotobacter can fix atmospheric nitrogen in the soil. (ii) Blue-green algae like Anabaena, Nostoc, Occilatoria add organic matter to the soil and responsible for increase its fertility.

Question. Name the scientists who were credited for showing the role of penicillin as an antibiotic?
Answer : Penicillin was discovered by Sir Alexander Fleming while, working on Staphylococci bacteria. However, its full potential as an effective antibiotic was established much later by Ernst Chain and Howard Florey. This antibiotic was extensively used to treat American soldiers wounded in World War II. Fleming, Chain and Florey were awarded the Nobel Prize in 1945, for this discovery.

Question. How do bioactive molecules of fungal origin help in restoring good health of humans?
Answer : Some bioactive molecules of fungal origin have been reported for their role in restoring good health of humAnswer : Cyclosporin-A, that is used as an immuno-suppressive agent in organ transplant patients is produced by the fungus Trichoderma polysporum. Statins produced by yeast Monococcus purpureus have been commercialised as blood cholesterol lowering agents.

Question. How do mycorrhizal fungi help the plants harbouring them?
Answer : The mycorrhizal fungi absorb phosphorus from the soil and transfer them to the host cells. They also impart resistance to host plants against root pathogens. They also show tolerance to salinity and draught as well as increases overall growth and development of plant. Hence, fungal hyphae help in synthesising organic food and also recieve/get shelter and nourishment from the higher plant.

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