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.