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Types of Micro-organisms Bacteria Viruses Fungi Protozoa.

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Presentation on theme: "Types of Micro-organisms Bacteria Viruses Fungi Protozoa."— Presentation transcript:



3 Types of Micro-organisms Bacteria Viruses Fungi Protozoa

4 fungi ( eg. Mucor, Rhizopus ) protozoa ( eg. Amoeba, Paramecium ) algae (unicellular / colonial form) ( eg. Spirogyra ) Algae - Diatoms Zooplankton (some multicellular)

5 Useful Micro-organisms yeast –carry out alcoholic fermentation in the presence of carbohydrates & the absence of O 2 baking bread produces carbon dioxide to raise the dough brewing beer / making wine fermentation to produce alcohol

6 nitrogen-fixing bacteria in leguminous plant [root nodules] –carry out nitrogen fixation which changes N 2 gas from the air to nitrogenous compounds for plants to produce protein Useful Micro-organisms

7 decomposers & nitrifying bacteria –decomposers decompose organic waste & dead body into ammonia –nitrifying bacteria change ammonia into nitrate for plants to make protein Useful Micro-organisms

8 Harmful Micro-organisms disease causing (pathogens) – bacterial disease : e.g. cholera, sore throat, tuberculosis – viral disease : e.g. AIDS, bird flu, common cold, influenza – fungal disease : e.g. athletes foot, ringworm – protozoa disease : e.g. malaria, sleeping sickness athlete's foot Dust Mite - multicellular

9 bacteria –prokaryotic cells (without nuclear membrane) –reproduce by binary fission –some are pathogenic, some are useful

10 viruses –with only DNA/RNA + protein coat –all are parasitic (they are considered living only when they are inside living cells)

11 decay food & other useful materials –microorganisms are saprophytic –take in decaying food: cause food poisoning Harmful Micro-organisms

12 chemicals produced by microorganisms which can kill or stop the growth of bacteria & fungi e.g. penicillin importance: effective in treating many diseases such as meningitis, syphilis, etc Antibiotics

13 Broad-spectrum antibiotics: can attack many different strains of bacteria Narrow-spectrum antibiotics can attack only one or a few strains of bacteria Antibiotics

14 Clear zone - indicates the absence of bacteria which had been killed by the antibiotic Antibiotics Clear zone with larger diameter indicates a more powerful antibiotic against the bacteria

15 Food Preservation Heating –kill most microorganisms & their spores by high temperature Canning & Bottling –sealing in cans to avoid bacterial entry –should work together with sterilization

16 Pasteurization –kill most microorganisms without changing the flavour of milk –75 for 15s and then quickly cooled & bottled UHT (Ultra High Temperature) treatment –common in killing bacteria in milk –superheat to ~150 for a few seconds and then sealed Food Preservation

17 Refrigeration –to decrease or stop the activities & growth of microorganisms (NOT killing them) Freezing –stop the activities of micro-organisms –NOT killing them –they can resume activity when ice melts Food Preservation

18 Drying (Dehydration) –micro-organism dies due to water deficiency Smoking –dry, coat with smoke which has chemical to stop bacterial growth Food Preservation

19 Pickling –add vinegar (usually together with salt) –kill bacteria by acid Osmotic preservation –by adding salt or sugar –to remove water from micro-organisms by osmosis Food Preservation

20 Irradiation –expose food to -radiation –kill bacteria and moulds & prevent food spoilage Preservatives –add to food to stop bacterial growth or kill them Food Preservation

21 ~ END ~

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