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Exam Ready Notes ::Micro-organisms

  1. microorganisms or microbes cannot seen without any suitable microscope
  2. Microorganisms are classified into four major groups. These groups are bacteriafungi protozoa  and some algae
  3.  Viruses are also microscopic. They, however, reproduce only inside the cells of the host organism, which may be a bacterium, plant or animal
  4. Common ailments like cold, influenza (flu) and most coughs are caused by viruses. Serious diseases like polio and chicken pox are also caused by viruses. 
  5. Diseases like dysentery and malaria are caused by protozoans whereas
    typhoid and tuberculosis (TB) are bacterial diseases.  
    ---------------- 
  •  Microorganisms may be single-celled like bacteria, some algae and protozoa, or multi-cellular, such as algae and fungi. They can survive under all types of environment, ranging from ice cold climate to hot springs and deserts to marshy lands. They are also found inside the bodies of animals including humans. Some microorganisms grow on other organisms while others exist freely. Microorganisms like amoeba can live alone, while fungi and bacteria may live in colonies.
  • Microorganisms are used for various purposes. They are used in the preparation of curd, bread and cake.
  • They are also used in cleaning up of the environment. For example, the organic wastes (vegetable peels, remains of animals,   faeces, etc.) are broken down into harmless and usable substances by bacteria. Recall that bacteria are also used in the preparation of medicines. In agriculture they are used to increase soil fertility by fixing nitrogen.  
  • They are also used in cleaning up of the environment. For example, the organic wastes (vegetable peels, remains of animals,   faeces, etc.) are broken down into harmless and usable substances by bacteria. Recall that bacteria are also used in the preparation of medicines. In agriculture they are used to increase soil fertility by fixing nitrogen.  
  •  They are also used in cleaning up of the environment. For example, the organic wastes (vegetable peels, remains of animals,   faeces, etc.) are broken down into harmless and usable substances by bacteria. Recall that bacteria are also used in the preparation of medicines. In agriculture they are used to increase soil fertility by fixing nitrogen.
  • Yeast  r epr oduces  rapidly  and produces carbon dioxide during respiration. Bubbles of the gas fill the dough and increase its volume This is the basis of the use of  yeast in the baking industry for making breads, pastries and cakes.
  • Commercial Use of Microorganisms
    Microorganisms are used for the large scale production of alcohol, wine and acetic acid (vinegar). Yeast is used for commercial production of alcohol and wine. For this purpose yeast is grown on natural sugars present in grains like barley, wheat, rice and crushed fruit juices, etc.  
  • some antibiotic tablets, capsules or injections such as of penicillin. The source of these medicines is microorganisms. These medicines kill or stop the growth of the disease-causing microorganisms. Such medicines are called antibiotics. These days a number of antibiotics are being produced from bacteria and fungi. Streptomycin, tetracycline and erythromycin   are   some   of   the    commonly known antibiotics which are made from fungi and bacteria. The antibiotics are manufactured by growing specific microorganisms and are used to cure a variety of diseases. Antibiotics are even mixed with the feed of livestock and poultry to check microbial infection in animals. They are also used to control many plant diseases.  
  • When a disease-carrying microbe enters our body, the body produces antibodies to fight the invader. The body also remembers how to fight the microbe if it enters again. So, if dead or weakened microbes are introduced in a healthy body,  the  body  fights  and  kills them by producing suitable antibodies. The antibodies remain in the body and  we are protected from the disease- causing microbes. This is how a vaccine works. Several diseases, including cholera, tuberculosis, smallpox and hepatitis can be prevented by vaccination
  • Some bacteria and blue green algae  are able to fix nitrogen from the atmosphere to enrich soil with nitrogen and increase its fertility. These microbes are commonly called biological nitrogen fixers  
  • microorganisms can be used to degrade the harmful and smelly substances and thereby clean up the environment
  • Microorganisms are harmful in many ways. Some of the microorganisms cause diseases in human beings, plants and animals. Such disease-causing    microorganisms are called pathogens. Some microorganisms spoil food, clothing and leather.
  • Microbial diseases that can spread from an infected person to a healthy person through air, water, food or physical contact are called communicable diseases. Examples of such diseases include cholera, common cold, chicken pox and tuberculosis.

  •  
    Table 2.1: Some Common  Human Diseases caused by Microorganisms

    Human Disease
    Causative
    Microorganism
    Mode of
    Transmission
    Preventive measures
    (General)

    Tuberculosis Measles Chicken Pox Polio

    Bacteria

    Virus Virus Virus

    Air Air Air/Contact Air/Water


    Keep the patient in complete isolation. Keep the personal belongings of the patient away from those of the others. Vaccination to be given at suitable age.

    Cholera

    Typhoid

    Bacteria

    Bacteria

    Water/Food

    Water

    Maintain personal hygiene and good sanitary habits. Consume properly cooked food and boiled drinking water. Vaccination.

    Hepatitis B

    Virus

    Water

    Drink boiled drinking water. Vaccination.

    Malaria

    Protozoa

    Mosquito
    Use mosquito net and repellents. Spray insecticides and control breeding of mosquitoes by not allowing water to collect in the surroundings.
     
  • Salts and edible oils are the common chemicals generally used to check the growth of microorganisms. Therefore they are called preservatives. We add salt or acid preservatives to pickles to prevent the attack of microbes. Sodium benzoate and sodium metabisulphite are common preservatives. These are also used in the jams and squashes to check their spoilage.   
  • Common salt has been used to preserve meat and fish for ages. Meat and fish are covered with dry salt to check the growth of bacteria. Salting is also used to  preserve  amla ,  raw  mangoes, tamarind, etc.  
  • Jams, jellies and squashes are preserved by sugar. Sugar reduces the moisture content which inhibits the growth of bacteria which spoil food
  • Use of oil and vinegar prevents spoilage of pickles because bacteria cannot live in such an environment. Vegetables, fruits, fish and meat are often preserved by this method
  • Pasteurized milk can be consumed without boiling as it is free from harmful microbes. The milk is heated to about 700C for 15 to 30 seconds and then suddenly chilled and stored. By doing so, it prevents the growth of microbes. This process was discovered by Louis Pasteur. It is called pasteurization.   
  • These days dry fruits and even vegetables are sold in sealed air tight packets to prevent the attack of microbes.  
  • Rhizobium lives in the root nodules of leguminous plants , such as beans and peas, with which it has a symbiotic relationship. Sometimes nitrogen gets fixed through the action of lightning 
  • nitrogen cannot be taken directly by plants and animals. Certain bacteria and blue green algae  present in the soil fix nitrogen from the atmosphere and convert into compounds of nitrogen. Once nitrogen is converted into these usable compounds, it can be utilised by plants from the soil through their root system. Nitrogen is then used for the synthesis of plant proteins and other compounds. Animals feeding on plants get these proteins and other nitrogen compounds
    When plants and animals die, bacteria and fungi present in the soil convert the nitrogenous wastes into nitrogenous compounds to be used by plants again. Certain other bacteria convert some part of them to nitrogen gas which goes back into the atmosphere. As a result, the percentage of nitrogen in the atmosphere remains more or less constant
  • Microorganisms are too small and are not visible to the unaided eye.
          They can live in all kinds of environment, ranging from ice cold climate to hot springs and deserts to marshy lands.
          Microorganisms are found in air, water and in the bodies of plants and animals.
          They may be unicellular or multicellular.
          Microorganisms include bacteria, fungi, protozoa and some algae. Viruses, though different from the above mentioned living organisms, are considered microbes.
          Viruses are quite different from other microorganisms. They reproduce only inside the host organism; bacterium, plant or animal cell.
         Some microorganisms are useful for commercial production of medicines and alcohol.
          Some microorganisms decompose the organic waste and dead plants and animals into simple substances and clean up the environment.
          Protozoans cause serious diseases like dysentery and malaria.
          Some of the microorganisms grow on our food and cause food poisoning.
          Some microorganisms reside in the root nodules of leguminous plants. They can fix nitrogen from air into soil and increase the soil fertility.
          Some bacteria and blue green algae present in the soil fix nitrogen from the atmosphere and convert into nitrogenous compounds.
                Certain bacteria convert compounds of nitrogen present in the soil into nitrogen gas which is released to the atmosphere.  
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