MICROORGANISMS
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Definition:
living organisms around us which cannot be seen by naked eyes is called
microorganism or microbes. We need a microscope to see microbes.
TYPES OF MICROORGANISMS:
There are five major groups of micro-organisms. These are classified as:
1. BACTERIA
2. ALGAE
3. PROTOZOA
4. FUNGI
5. VIRUSES
1.1) bacteria:
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Mostly single celled organism.
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Lived together in colonies of millions.
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Found in basically 3 different shapes:
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Rod shaped(bacilli)
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Spherical shaped (cocci).
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Spiral (spirillia).
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Rod shaped(bacilli)
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Spherical shaped (cocci)
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Spiral (spirillia)
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2.2) algae:
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Simple plant like structure organism.
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Aquatic in nature.
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It can be unicellular or multicellular.
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Ex: chlamydomonas, seaweed, diatoms.
3.3) protozoa:
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Unicellular microorganism.
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Mostly aquatic in nature.
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Ex- amoeba, paramecium etc.
4.4) fungi:
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Plant like organism that do not contain chlorophyll
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Can be unicellular or multicellular. Ex- yeast, rizopus etc.
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Bread Mould
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Penicillium
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Aspergillus
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5.5) viruses:
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Smaller than any other known cell.
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It can reproduce only inside living bodies, means they need a host.
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It is a borderline between a living and non living thing.
FRIENDLY MICRO-ORGANISMS
USES
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Used in preparation of curd, bread and cake.
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Used in cleaning up of the environment by degrading dead and decay
substances.
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Used in increasing soil fertility by fixing nitrogen.
MAKING OF CURD, CHEESE AND BREAD
Bacterium lactobacillus promotes the formation of curd. It multiplies in
milk and converts it into curd.
Bacteria convert the natural sugars in milk into lactic acid. Different
flavour of milk is due to different types of bacteria used.
Yeast
: used in making cakes and bread. Bakers add yeast to dough to increase its
volume by filling the gap by bubbles of carbon dioxide produced by yeast.
COMMERCIAL USE OF MICRO-ORGANISMS
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Used for large scale production of alcohol, wine and vinegar (acetic
acid).
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Yeast is used for commercial production of alcohol and wine.
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Fermentation- the process of conversion of sugar into alcohol by yeast is
known as fermentation.
MEDICINAL USE OF MICRO-ORGANISMS
Antibiotics
: these are the medicines that are used to treat infections caused by other
bacteria and certain parasites. Antibiotics are produced by the help of
other bacteria.
Example: Tetracycline, streptomycin, penicillin, erythromycin etc.
INCREASING SOIL FERTILITY
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Bacteria and blue green algae are able to fix nitrogen from the
atmosphere.
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Enrich the soil with nitrogen and increase its fertility.
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These microbes are called as biological nitrogen fixers.
CLEANING THE ENVIRONMENT
- Micro-organism converts dead and decaying part of plants and animals into
manures.
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It decomposes organic waste into simple substance.
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It degrades the harmful substance and cleans up the environment.
HARMFUL MICROORGANISMS
Some microorganisms are not good for us are called harmful microorganism.
Disease causing microorganisms in humans, plants and animals are called pathogens.
Diseases- causing Microorganisms in Humans
Pathogens are present everywhere.
Transferred to our body through - air, water and food or by direct
contact with infected body.
There are some insects and animals which act as carrier of disease
causing microbes.
Diseases that are transferred from unhealthy or infected person to
healthy person are called communicable disease.
EXAMPLE:-
- MALARIA- cause by the female anopheles mosquito that act as the carrier of malaria.
- DENGUE - female Aedes mosquito acts as carrier of dengue virus.
FOOD POISONING
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It occurs due to contaminated food products.
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Microorganism that grows on food product sometimes produce toxic elements
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Serious illness or even death may cause due to food poisoning.
Some common human diseases caused by microorganisms
Diseases- causing Microorganisms in Animals
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Anthrax is a dangerous human and cattle disease caused by a bacterium.
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Foot and mouth disease of cattle is caused by a virus.
Diseases- causing Microorganisms in
plants
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Disease in plants reduces the yield of crops.
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Example - citrus canker caused by bacteria, rusting of wheat by fungi
attack, etc.
METHODS OF FOOD PRESERVATION
Let us study some common method of food preservation in our homes.
CHEMICAL METHOD
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Chemicals are used to protect the food from being spoilt are known as
preservatives.
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We add salt or acid to pickles to prevent the attack of microbes.
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Sodium benzoate and sodium metabisulphate are common preservative.
PRESERVATION BY COMMON SALT
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Used to preserve meat and fish for ages.
- Meat and fish are covered to check the growth of bacteria.
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It is also used to preserve amla, raw mangoes, tamarind, etc.
PRESERVATION BY SUGAR
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Jams, jelly and squash are used to preserve by sugar.
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Sugar reduces the moisture content which inhibits the growth of bacteria.
PRESERVATION BY OIL AND VINEGAR
- Oil and vinegar create unfavourable conditions for the growth of
microorganisms.
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It is used to preserve fish, fruit, pickles and meat.
HEAT AND COLD TREATMENT
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Both higher and lower temperature prevents the growth of microorganism.
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By boiling or by keeping the food in refrigerator kills the microbes.
Pasteurization - heating of food to high temperature and then suddenly chilled and stored is called pasteurization.
It is done to kill and control the growth of bacteria.
NITROGEN FIXATION
In leguminous plant, RIBOZOBIUM helps in the fixation of atmospheric
nitrogen. Sometimes nitrogen gets fixed through the action of lightning.
NITROGEN CYCLE
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Our atmosphere has 78% of nitrogen gas.
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Nitrogen constituents as part of proteins, chlorophyll, nucleic acids and
vitamins.
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Amount of nitrogen in the atmosphere remain constant.
LET US SEE THE PROCESS BY WHICH THE NITROGEN IN ATMOSPHERE REMAINS
CONSTANT.
Nitrogen already present in atmosphere => bacteria likeblue green algae fixes atmospheric nitrogen in the soil=> from the soil nitrogen is used by plants => animals get protein and nitrogen from plants by
eating them => when animals and plants die bacteria and
fungi decomposes them and converted into nitrogenous compounds => some bacteria convert this nitrogenous compound into
nitrogen gas which ultimately goes back to atmosphere.