Chapter 17: Microorganisms and their Applications in Biotechnology

Viruses

• Not considered as cells - no protoplasm.

• Live on host cell.

• When they are living on host cell they are considered as living thing.

• They do not feed, respire, excrete, grow or reproduce - but; inside a host cell, virus can reproduce or replicate.

• Viral diseases and our defence system:

  • cold, influenza, chickenpox, dengue, haemorrhagic fever, herpes and AIDS.

  • can only be destroyed by antibodies produced by our WBCs.

Bacteria

• Living cells.

• Larger than viruses.

• Non-motile.

• Posses hair like threads called flagella.

• Three general types:

  • Cocci - spherical shaped

  • Bacilli - rod shaped

  • Spirilla - spiral shaped

• Bacteria can be:

  • Saprophytic - feeding on decaying organic material.

  • Parasitic - causing diseases in plants and animals.

  • Autotrophic - able to manufacture food using energy from the sun or inorganic material.

Fungi

• Live as saprophytes.

• Unicellular e.g yeast or multicellular e.g bread mould.

• Parasitic fungi live on the living tissue of their hosts.

Role of microorganisms in decomposition

• Decomposers in nature

  • Decomposers feed on dead and decaying organisms and their faeces.

  • They secrete enzymes which break down complex organic compounds to simple organic compounds.

  • They absorb small amount of energy and nutrients; most of the energy is lost as heat and the remaining nutrients are released into surrounding.

  • Inorganic compounds compounds release gases like CO2, hydrogen sulphide and water vapour.

  • Help maintain life on earth.

• Decomposers in sewage:

  • Decomposed by saprophytic microorganisms.

  • Bacteria in sewage secrete an enzyme to digest solid organic matter into soluble harmless substances.

Biotechnology

• Fermentation

  • Yoghurt making

    • By fermenting milk and using lactobacillus bulgaricus (bacteria).

    • In the absence of O2 bacteria respires anaerobically and converts lactose to lactic acid .

    • This acid curdles the milk producing yogurt, it can later be flavored or sweetened.

  • Cheese making

    • Use both bacteria and fungi.

    • Lactobacillus is used to ferment milk sugar to lactic acid. The mixture curdles milk protein.

    • Curdled protein together with the fats in the milk, is removed and acted upon by a mixture of bacteria and fungi to produce cheese.

    • By different temperatures and different variation of bacteria and fungi different kind of cheese is produced.

  • Production of alcohol

    • Yeast is used for brewing.

    • Yeast is mixed with sugar.

    • Yeast starts to respire anaerobically to produce alcohol and carbon dioxide from sugar.

Antibiotics

• Complex substances produced by microorganisms.

• Used in treatment of bacterial infections.

• Commercial production.

• Penicillin production.

  

  Single-cell protein

  • eg. bacteria and yeast.

  • Help produce animal feed and human food.

Industrial Biotechnology

• Fermenters

  • Designed to keep its inside environment favourable for the desired biological process.

  • Designed for aerobic and anaerobic processes both.

  • Important features:

    • Cooling system

      • Removal of heat during microbial activities.

    • aeration system

      • For proper mixing ad adequate aeration.