1. Chapter-2 Microorganisms Class VIII Science

2. Objectives: To create a definition of microorganisms To know various types of microorganisms. To know about the science of studying microorganism. To know about device used to study microorganisms. Understanding and analyzing effects of microorganisms. Application of the concept in prevention from diseases and processing of food. Awareness towards pathogens and useful microorganisms.

3. Introduction  There are many living organisms in our surroundings, some are as huge as a Blue whale whereas some are as small as mycoplasma.  Tiny organisms which cannot be seen through naked eyes are called MICROORGANISM.  Science that deals with study of microorganism is called MICROBIOLOGY.  Microorganisms can occur at great depth in an oceans, in streams, in the snow of polar regions, in hot springs and even sulphur springs.  Soil may contain 50 million types of bacteria excluding other types of microbes.

4. Types of Microbes AlgaeFungi Bacteria Virus Protozoa

5. Various Microorganisms Other Microorganisms Viruses

6. Bacteria Simplest and very small living things Single-celled ; can be found almost, everywhere, prokaryotes. Nearly 2,50, 00,00,000 bacteria can exist in one gram of garden soil. Can exist in four shapes u (adjacent fig.) Some are autotrophic, others are heterotrophic. Reproduce by binary fission, form endospore during unfavorable condition.

7. Virus Different from rest microbes as they cant exist independently. On the borderline of being living and non living. Grow and multiply only inside the living cells of plants and animals. Found in variety of shapes. All known viruses cause diseases.

8. Plant-like simple organisms, contain chlorophyll May be Unicellular or Multicellular May be filamentous or branched, May be green, red or brown depending on what pigment they have. They are aquatic plants found in both fresh water and marine water. They are called grass of water as they float on the surface of stagnant water. They are autotrophic. Algae

9. Fungi Plant-like organisms, do not contain chlorophyll. May be Unicellular (yeast) or Multicellular (moulds). Plant body is called mycelium. Root like structure arise from base is called hypha. Mode of nutrition is saprophytic or parasitic. Grow on damp, warm, dark places or on dead and decayed organic matters, excreta, rotting fruits, leather goods, cooked vegetables, etc Also grow on or inside the bodies of living plants or animals. Reproduce asexually or sexually. Eg: Penicillium, mushrooms, etc.

10. Protozoa: Primitive animals Simple, minute, unicellular microscopic animals. Can be found in any favourable aquatic environment such as freshwater lakes, pools, ditches, stagnant ponds, moist soil, or in the bodies of animals including man as parasites. Nutrition is saprophytic or parasitic. Movement by flagella, pseudopodia or cillia. Reproduce asexually by budding, binary fission or spore formation.. Eg: Giardia, Euglena, Codosiga, etc.

11. Harmful Microorganisms Staphylococci and Clostridium botulinum cause food poisoning. Bacillus anthracis causes anthrax Amanita a beautiful mushroom is poisonous to eat. Puccinia & Ustilago cause rusts & smuts. Chrococcus & Oscillatoria produce toxins that effects nervous system of fish, birds, marine mammals, humans.

12. Useful Microorganisms Fungi Yeast is used in brewery and bakery. Organic acids like oxalic acid and citric acid are prepared by fungi.. Common edible fungi include Morchella, Agaricus, Ramaria, Clavaria and Plurotus. Yeast is a source of Vit- B complex. Antibiotics like Penicillin and Griseofulvin are extracted from Penicillium notatum and Griseofulvum respectively. Bacteria Many well known Antibiotics like streptomycin, aureomycin and chloromycetin, serum and vaccines are prepared with the help of bacteria. Mycoderma aceti help in producing vinegar or acetic acid. Escherichia coli synthesise vitamin B- complex. Help in sewage disposal.by putrefaction. Azatobacter, clostridium and rhizobium help in Nitrogen fixation. Nitrosomonas bacteria help in nitrification. Bacteria help in tanning of leather, acetone, lactic acid, alcohol production, etc.

13. Algae: Importance Chlorella yields an important antibiotic called chlorellin. Agar and algin are obtained from red and brown algae used in preparation of medicines and cosmetics. Brown agae are the sources of sodium, potassium and iodine. Iodine is obtained from alga called kelp. Nostoc and Anabaena are important in nitrogen fixations. Porphyra(red alga) is used as food in China and Japan Dried Chondrus is used in puddings and jellies in Ireland. Laminaria (sea weeds) are used as fodder for sheep and cattle. Chlorella(green alga) is very rich in protein and vitamins.

14. Food Preservation Bacteriocidal Method Irradiation Canning Bottling Vacuum Drying Bacteriostatic Method Dehydration Salting Adding Oil and Vinegar Deep Freezing Advantages It prevents the food from being spoiled by the action of enzymes It increases the storage period of food materials. It helps in obtaining the off-season food materials. It makes the transportation of food materials easier.

15. Nitrogen Cycle Root nodules in the roots of pea plant

16. SUMMARY

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