CBSE Class 12 Biology Microbes In Human Welfare Notes Set A

Download CBSE Class 12 Biology Microbes In Human Welfare Notes Set A 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

•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.



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.

oAvailable is sachets, mixed with water and sprayed on plants.
oEaten by insect larva
oToxin released in gut kills larvae.
• Now Bt toxin genes introduced into plants – resistant to insect pests.

e.g. Bt cotton.
• Tungus 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, Flocs sediments form – activated sludge(A.S.),Poured into sludge digester(small amount of A.S. used as inoculum) Filtration & sedimentation

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