Back to Lesson

• Microorganisms / Microbes: Living creatures which are not visible to the naked eye.
• Microscope :Device to observe microorganisms
• Classification of microorganisms:
  • Microorganisms are classified into fungi, protozoa, bacteria and algae.
  • Viruses are also kind of microorganisms, which are considered to be at border of living and non living organisms. Viruses live in host cell.
  • Diseases caused by viruses are: Cold, Influenza, Polio, Chicken pox, etc.
  • Unicellular microorganisms [Single cell]: Bacteria, some algae, protozoa
  • Multicellular microorganisms [Many cells]: Fungi and algae.
• Habitat of microorganisms:
  • Microorganism are found in air, land and water.
  • Microorganisms have the ability to survive in ice cold climate, hot springs, marshy lands, etc.
  • Microorganisms like plasmodium lives in human blood whereas, microorganisms like algae are free living. Fungi and bacteria lives in groups.

Click here to watch video on Classification And Habitat Of Microorganisms

• Friendly microorganisms:
  • Lactobacillus – Making of curd: When curd is added to milk, lactobacillus bacteria multiply themselves rapidly thereby converting milk into curd. Curd is also added to idli batter or in dough of bhatura in which bacteria multiplies releasing carbon dioxide. This makes them soft and puffy.
  • Yeast – Fermentation: Natural sugars from grains like wheat, barley and from crushed fruit juices is converted into alcohol by yeast. Process of conversion of sugar into alcohol is called fermentation.
  • Bacteria / Fungi – Medicines: Antibiotics [anti – against, biotic – organisms] are medicines which stops growth of microbes in the body. E.g. Streptomycin, tetracycline, erythromycin, penicillin. Antibiotics are generally produced by bacteria and fungi.
  • Vaccination: Immune system in our body have the ability to fight against the harmful microbes entering into the body and remembering them. In process of vaccination, dead or weak microbes of disease are entered into the body. Our body fights with these organisms and remembers it. When real and strong microbes enters into the body remembers it by fight with more power and thereby curing the disease in less time.
  • Blue green algae / Rhizobium – Increasing soil fertility: Bacteria like blue green algae and rhizobium fixes atmospheric nitrogen by the process of nitrogen fixation, thereby increasing fertility of soil.
  • Cleaning the environment: Microorganisms decompose dead organic waste from the surrounding thus, keeping environment clean.
• Harmful Microorganisms(Pathogens):
  • Pathogens enters into the body through air, water, food or by coming in contact with infected person.
  • Communicable diseases: Diseases which get transferred from infected person to healthy person is called communicable disease.
  • Air borne disease: Diseases which gets transmitted through air is called air borne diseases. E.g : Tuberculosis, Measles, Chicken Pox, Polio, Common Cold, etc. vaccination is also used to cure airborne disease. To prevent such disease one must use handkerchiefs while sneezing.
  • Water borne diseases: Disease which are transmitted through water is called water borne disease. E.g: Cholera, Typhoid, Polio, Hepatitis B, etc. To prevent such disease one must maintain personal hygiene and drink boiled water.
  • Disease transmitted by carrier: Carriers are the living organisms which carry pathogens with them. E.g. house flies, mosquitoes, etc.
  • Disease causing microorganisms in animals: Bacteria causes disease anthrax in humans and cattles. Viruses cause foot and mouth disease in cattles. Vaccination prevents such diseases.
  • Disease causing microorganisms in plants: Plant can catch disease transmitted through through air, seeds or insects. Cause of disease can be virus, bacteria or fungi. E.g. Citrus Canker, Rust of wheat, Yellow vein mosaic of Okra, etc.

Click here to watch video on Friendly And Harmful Microorganisms

• Food Poisoning: Harmful microbes secrete toxic substances on food after attacking it. If this food is eaten by humans, it may lead to severe consequence, or even lead to death. To avoid this food must be preserved.
• Food preservation:
  

  Method of preservation	Main component / Procedures	Examples
  Chemical method	Sodium benzoate, sodium metabisulphite	Prevents jams, squashes, etc from spoilage
  Common Salt	Common salt	Prevents growth of bacteria on meat and fish
  Sugar	Sugar	Prevents by reducing moisture in jams, jellies, squashes, etc
  Oil and vinegar	Oil, vinegar	Prevents growth of bacteria on vegetables, fruits, fish, meat, etc
  Heat and cold treatments	Heating, freezing	heating kills microorganisms and freezing or keeping at low temperatures prevents their growth/td>
  Pasteurisation	Heating and cooling	Milk is heated at 700 ° C and then suddenly cooled which makes milk free from bacteria and prevents growth.
  Storage and packing	Airtight containers/ packets	Prevents growth of microorganisms in dry fruits, vegetables,etc

• Nitrogen Fixation: Atmospheric nitrogen is converted to nitrogen compounds by bacteria like blue green algae, rhizobium. The process is known as nitrogen fixation. Rhizobium lives in root nodules of leguminous plants. Lightning also fixes atmospheric nitrogen.
• Nitrogen Cycle:
  • When atmospheric nitrogen is fixed, it s converted to compounds and are absorbed by plant roots.
  • Plants uses these compound in synthesis of different nitrogen compounds.
  • Animals use these compound from plants.
  • Plants and animals die, bacteria and fungi present in soil convert & decompose them into nitrogenous compounds.
  • These are absorbed by roots of plants.
  • Excess of nitrogen is again passed back to atmosphere with help of certain bacteria.