Microorganisms-Friend And Foe


Microorganisms-Tiny organisms , microscopic, living, single-celled organisms which can’t be seen with unaided eye. 

Micro-organisms are of great importance to the human health , to environment, and to our economy.There are useful as well as harmful microorganisms.

               Robert Koch(1876)

Discovered the bacterium(Bacillus anthracis)which causes     anthrax disease
Why microorganisms are called microorganisms ?

 Microorganisms can’t be  seen with unaided eye .To see microorganisms we need microscopes and in some cases magnifying glass that is why microorganisms are called microorganisms .

Microorganisms are categorized into four major groups .

Four groups in which microorganism are grouped a  Fungi,  Bacteria,  Algae and Protozoa.

Viruses- Viruses consist of genetic materials (DNA or RNA) surrounded by a protective coat of protein.
  •  Viruses are microscopic and too small to be seen by the naked eye.
  • Viruses can't multiply on their own they reproduce only inside host organism,host may be plants animals or bacterium.
  • Viruses consist of genetic materials (DNA or RNA)
  • Virus is inactive when outside the host organism and become active inside host organisms.

Human diseases which are caused by viruses. 

These include:
        Smallpox
        The common cold
        Measles
        Chickenpox
        Hepatitis
        Influenza
        Polio
        Rabies
        HIV (the virus that causes AIDS)
        SARS (Severe acute respiratory syndrome)
        Dengue

Diseases caused by bacteria
Typhoid Fever,
Leprosy (Hansen's Disease) ,

Diseases caused by protozoa(Protozoans) 
Sleeping Sickness

Habitats of microorganisms

  • Microorganisms live in all place which you know .
  • Microorganisms live in extreme conditions where we can’t live ranging from hot springs to  ice cold climate and from marshy lands to deserts. 
  • Microorganism even live in human body .

Some microorganisms are beneficial for us and some microorganism are harmful for us,plants and animals.

Good microorganisms-If microorganisms are good for us they are called good microorganisms.

Bad microorganisms-If microorganisms causes disease or creates other problems for us they are called bad microorganisms.

Benefits of Microorganisms to Humans

             Edward Jenner

Discovered the vaccine for small pox in 1798

Uses of microorganisms

Friendly microorganisms
Friendly microorganisms are useful for us because they helps in cleaning environment by degrading dead and decay substances,microorganisms are used in increasing soil fertility.microorganism are used in making cake, bread and curd etc

Making curd and Bread
Lactobacillus Bacteria helps in the formation of curd from milk.

How milk is converted into curd ?

Lactobacillus denatures the structure of protein  casein  present in milk by producing Lactic acid it destroys the tertiary and quaternary structures of proteins  thus globular protein is converted into fibrous protein which gives thick textures to the milk due to the coagulation of proteins.
By this process milk is converted into curd.

Bacteria help in making cheese
Bacteria convert the natural sugars in milk (lactose) into lactic acid. Different flavor of the milk is due to the different types of bacteria used.
Bacteria also helps in making pickles and other food products.

Yeast (fungi –one of the group of microorganisms)
Uses of microorganisms,yeast in making cakes, breads, pastries in baking industry.
Bakers add yeast to dough ,yeast reproduces very fast and produces carbon dioxide during respiration.Bubles of the gas produced fills the dough  and increases its volume.

Commercial use of Microorganisms.
Commercially microorganisms are used for making wine ,alcohol and acetic acid(vinegar).

Wine and Alcohol are commercially produced by using Yeast (Fungi).
                  Louis Pasteur 
Discovered fermentation in 1857
Microorganism yeast is grown on natural sugars present in crushed fruit juices,wheat,barley,rice etc and by the process of fermentation yeast convert sugars into alcohols.

Fermentation-the process of conversion of sugars into alcohol is known as fermentation.

Medicinal use of microorganisms

What is antibiotic?

Antibiotics -Antibiotics are a group of medicines that are used to treat
infections caused by bacteria and certain parasites.
Antibiotics are produced by the uses of bacteria.

Examples of antibiotics-Tetracycline,Streptomycin,erythromycin, Doripenem, Daptomycin, Clarithromycin, Penicillin G, Penicillin V etc

Uses of microorganisms in Increasing soil fertility
Bacteria (Biological nitrogen fixers)like blue green algae  fixes atmospheric nitrogen and convert it in other forms of nitrogen that is used by plants thus it enrich soils with nitrogen and increases the soil fertility.

Uses of microorganisms in Cleaning Environment
Microorganism converts dead and decaying  parts of plants and animals into manure  by decomposing them into simple substance.Thus the microorganism clean up the environment.

Harmful microorganisms

Microorganisms which are not good for us are called harmful microorganisms.
Microorganisms causes disease in animals ,human beings and plants therefore they are  also called pathogens.

Pathogens-Disease-causing microorganisms are called pathogens.

Diseases causing microorganisms in Humans
Pathogens presents everywhere. Pathogens transferred into our body from air, water and food or by direct contact with infected person or animal.

Malaria-Female anopheles mosquito carries parasite of  malaria.

Dengue virus-Female Aedes mosquito acts as carrier of Dengue virus.

Communicable diseases

what is communicable disease ?
Diseases which transferred from unhealthy or infected person to healthy person are called communicable diseases.Communicable disease may be spread through air,water,soil, etc

Examples of communicable disease

Sexually Transmitted Disease 

Food  poisoning –Food poisoning is occurred due to the contaminated food products. Microorganism which grows on food sometimes produces toxic substances this may cause serious illness or even death this are called food poisoning.

So the preservation of food is necessary to prevent it from being spoilt.

Food Preservation and Techniques of Food preservation.

Modern preservatives

Methods of food preservation.

Chemical Method of food preservation-Some chemicals  are used to protect the food from being spoilt these are called Preservatives. 

  • Salt and edible oils are the most common chemical preservatives .
  • Sodium metabisulphite and sodium benzoate are common preservatives.

Preservation by common Salt-Common salt is used to preserve meat and fishes , common salt is spread over meat and fishes to check the growth of bacteria. Common salt is also used in the preservation of tamarind, raw mangoes and amla etc.

Preservation by Sugar-Sugar is very useful preservative for the preservation of squashes, jams and jellies. Sugar controls the growth of bacteria by reducing moisture content.

Preservation by Oil and Vinegar-Oil and vinegar create unfavorable conditions for the growth of microorganisms. Therefore Oil and vinegar is used to preserve fish, fruit, pickles and meat.

Heat and Cold Treatment-Both higher and lower temperature prevents the growth of microorganisms. Boiling does not allow to grow microbes by killing them. In similar way food kept in lower temperature such as refrigerator inhibits the growth of microorganism.


what is pasteurisation ?
Heating of milk (a food, as cheese, yogurt etc) to high temperature  and then suddenly chilled and stored is called pasteurisation.

Pasteurisation is done to kill and control the growth of bacteria  that can produce disease or cause spoilage or undesirable fermentation of food .

Storage and Packing-Food products are sealed in air tight container or packets to prevent the food from microbes. Dry fruits and vegetable are preserved by this method.

Nitrogen Fixation-Rhizobium helps in the fixation of atmospheric nitrogen in leguminous plants (pulses).

Nitrogen cycle

  • Our atmosphere has 78% of nitrogen gas.
  • Nitrogen constitutes part of protein in living beings .
  • Amount of nitrogen in the atmosphere remains constant.

How the amount of nitrogen in the atmosphere remains constant?

Process which shows the amount of nitrogen in the atmosphere remains constant-

Nitrogen in atmosphere=>Some bacteria like blue green algae fixes atmospheric nitrogen in the soil=>From the soil nitrogen is used by plants=>Animals get protein and nitrogen from plants after eating them.=>When animals and plants die bacteria and fungi decomposes them and converted into nitrogenous compounds=>Some bacteria converts these nitrogenous compound into nitrogen gas which ultimately goes back to atmosphere.

Above nitrogenous compound is used by plants again.
Nitrogen cycle

These process goes on and on thus the amount of nitrogen in the atmosphere remains constant.

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