Notes for Microbes in Human Welfare - 12th Biology
MICROBES IN HUMAN WELFARE
MICROBES ARE PRESENT EVERYWHERE. IN SOIL, AIR , WATER
ETC ALSO IN EXTREME CONDITIONS, EXTREMOPHILES
MICROBES ARE GROWN IN MEDIA TO FORM COLONIES, SEEN
WITH NAKED EYE.
Microbes are diverse – protozoa, bacteria, fungi and microscopic plants
viruses, viroids and also prions (proteinocious infectious agents)
What is Microbiology?
• Micro - too small to be seen with the naked eye
• Bio – life
• logy - study of
• It is the study of very small living organisms called
Applications of Microbiology
• Food production: bread, beer
• Microbes a s a source of food (SCP)
• Microbes in biogas production
• Microbes as biocontrol agents
• Microbes as biofertilizers
• Bioremediation: decontamination of hazardous wastes
• Useful industrial products: ethanol fuel, antibiotics, amino acids
• Genetic engineering: pharmaceuticals, vaccines
• Microbes in sewage treatment
MICROBES IN HOUSEHOLD PRODUCTS:
Lactic acid Bacteria (LAB) grow in milk and convert it to curd.
LAB produces acids that coagulate and partially digest milk proteins.
LAB improves nutritional quality of milk by increasing vitamin B12
LAB plays very important role in checking disease causing microbes.
Dough, used to make dosa and idli is also fermented by bacteria.
The puffed-up appearance of dough is due to the production of CO2.
Baker’s yeast (Saccharomyces cervisiae) is used to making bread.
Large holes in ‘Swiss cheese’ are due to production of large amount
of CO2 by a bacterium named Propionibacterium sharmanii.
The ‘Roquefort cheese’ is ripened by specific fungi, which gives
MICROBES AS SOURCE OF FOOD:
SCP (SINGLE CELL PROTEIN)- It refers to the microbial biomass or
total protein total extracted from pure microbial cell culture(monoculture)
which can be used as protein supplement. It is used because:•
.They have HIGH protein & LOW fat content.
It is good source of vitamins particularly Bcomplex.
It can be produced through-out the year.
Waste materials are used as substrate for the
production of these proteins.
SCP organisms grows faster.
The quality & quantity of protein content in
micro-organism is better compared to higher
plants and animal.
Examples of edible of mushrooms:
MICROBES IN INDUSTRIAL PRODUCTS:
Microbes are used in industry to synthesize a number of products
Beverages, enzymes, organic acids, vitamins and antibiotics are some
Microbes are grown in very large vessels called fermenters.
Yeasts are used for production of beverages like wine, beer, whisky,
brandy or rum.
Saccharomyces cervisiae commonly called ‘brewer’s yeast used for
fermenting malted cereals and fruit juices to produce ethanol.
The type of raw material used for fermentation and the processing,
different types of alcoholic drinks are produced.
Wine and beer are produced without distillation.
Whisky, brandy and rum are produced by distillation of the
Antibiotics are the chemical substances which are produced by some
microbes and can kill or retard the growth of other microbes.
The first antibiotic discovered is the penicillin, from a mould
(fungus) Penicillium notatum.
Antibiotics have greatly improved our capacity to treat deadly
diseases such as plague, whooping cough. Diphtheria and leprosy.
List of antibiotics
Name of antibiotic
Chemicals, Enzymes and other Bioactive Molecules:
Aspegillus niger (a fungus) produces citric acid.
Acetobacter aceti (a bacterium) produce acetic acid.
Clostridium butylicum (a bacterium) produce butyric acid.
Lactobacillus(a bacterium) produces lactic acid.
Lipases are used in detergent produced by microbes.
Pectinase, proteases and cellulase, make bottled fruit juices clearer.
Streptokinase produced by Streptococcus used as a ‘clot buster’, for
removing clots from the blood vessels.
Cyclosporin-A produced by a fungus called Trichoderma
Statins produced by Monascus purpureus used as blood cholesterol
lowering agents. It acts as competitive inhibitor for the enzyme
responsible for synthesis of cholesterol.
Gibberellins are produced in greater mass by soil fungi Gibberella
Some commercial enzymes and source microorganisms:
MICROBES IN SEWAGE TREATMENT:
The waste water generated in cities and town containing human
excreta. This municipal water-water is called sewage.
Before disposal to the natural body sewage is treated in sewage
treatment plants (STPs) to make it less polluting.
Treatment is done by heterotrophic microbes naturally present in
Involves the physical removal of particles – large and small from
sewage through filtration and sedimentation.
Initially floating debris is removed by sequential filtration.
The grit (soil and small pebbles) are removed by sedimentation.
All solids that settle form the primary sludge, and the supernatant
forms the effluents.
The effluents are from the primary settling tank taken for secondary
Secondary treatment or Biological treatment:
The primary effluent is passed into large aeration tanks.
This allows vigorous growth of useful aerobic microbes intoflocs.
The growth of microbes consumes the major part of the organic
matter in the effluent. This significantly reduces the BOD
(biochemical oxygen demand) of the effluent.
BOD refers to the amount of oxygen required to oxidize total organic
matter by bacteria, present in one liter of water.
BOD is the measures of the organic matter present in the water.
Greater the BOD of the waste water more is its polluting
Once the BOD of sewage reduced significantly, the effluent is then
passed into the settling tank where the bacterial ’flocs’ are allowed to
sediment. This sediment is called activated sludge.
Small part of activated sludge is pumped back to aeration tank to
serve as the inoculums.
The remaining sludge is pumped into anaerobic sludge digester.
In the anaerobic sludge digester there is other kinds of bacteria which
grow anaerobically, digest the bacteria and fungi in the sludge.
During this digestion bacteria produce biogas, (mixture of methane,
hydrogen sulphide and carbon dioxide)
The effluent from the secondary treatment plant is released into
natural water body like rivers and streams.
Ganga Action Plan and Yamuna Action Plan initiated by Ministry
of Environment and Forest to save these major rivers of our country.
It is proposed to build a large number of sewage treatment plants so
that only treated sewage may be discharged into the rivers.
MICROBES IN PRODUCTION OF BIOGAS:
Biogas is a mixture of gases (predominantly methane) produced by
the microbial activity and is used as fuel.
Certain bacteria grow anaerobically on cellulosic material, produce
large amount of methane along with CO2 and H2S. These bacteria are
called methanogens. One
These bacteria present in the rumen of cattle, plays essential role in
nutrition of cattle by digesting cellulose. Hence the excreta (dung)
used for the production of biogas.
This is a multistep biological and chemical process that is beneficial in not
only waste management but also energy creation. There are four
fundamental steps of anaerobic digestion that include hydrolysis,
acidogenesis, acetogenesis, and methanogenesis. Throughout this entire
process, large organic polymers that make up Biomass are broken down into
smaller molecules by chemicals and microorganisms. Upon completion of
the anaerobic digestion process, the Biomass is converted into Biogas,
namely carbon dioxide and methane, as well as digestate and wastewater.
The whole biogas-process can be divided into three steps: hydrolysis,
acidification, and methane formation.
Biogas microbes consist of a large group of complex and differently acting
microbe species.Three types of bacteria are involved :
Pseudomonas, Clostridium, Methanococcous and Methanobacillus spp.
MICROBES AS BIOCONTROL AGENT:
Biocontrol refers to the use of biological methods for controlling plant
diseases and pests.
Effect of use of chemical, insecticide and pesticide to control disease
o These chemicals are toxic and extremely harmful to human
beings and animals
o Polluting our environment (soil, ground water), fruits, and
o Soil is polluted through use of weedicides to remove weeds.
Biological control of pest and disease:
Use of biocontrol measures will greatly reduce our dependence on
toxic chemical and pesticides.
The Ladybird and Dragonflies are used to get rid of aphids and
Bacillus thuringiensis (Bt) used to control butterfly caterpillars.
Dried spores are mixed with water and sprayed onto vulnerable plants,
where these are eaten by the insect larvae.
In the gut of the larvae, the toxin is released and the larvae get killed.
Trichodermaa free living fungus used to control several plant
Baculoviruses are pathogen that attack insects and other arthropods
The majority of baculoviruses used as biological control agents are in
the genus Nucleopolyhedrovirus.
These viruses are excellent candidates for species-specific, narrow
spectrum insecticidal application.
They have no negative impacts on plants, mammals, birds, fish, etc.
This is very use full in integrated pest managements (IPM).
MICROBES AS BIOFERTILIZERS:
Biofertilizers are organisms that enrich the nutrient quality of the soil.
Main biofertilizers are the bacteria, fungi and cyanobacteria.
Rhizobiumform root nodules in legumes and fix atmospheric
Azospiriliumand Azotobacter free living bacteria fix atmospheric
nitrogen and thus increasing nitrogen content of the soil.
Mycorrhiza: fungi symbiotically associated with root of plants.
o Provide phosphorus to the plants from the soil.
o Make the plant resistant to root-borne pathogen.
o Increase tolerance to salinity and drought.
Cyanobacteria like Anabaena, Nostoc, and Oscillatoria etc:
Fix atmospheric nitrogen.
add organic matter to the soil and
Increase soil fertility.
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