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Types of Micro-organisms

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Presentation on theme: "Types of Micro-organisms"— Presentation transcript:


2 Types of Micro-organisms
Bacteria Viruses Fungi Protozoa

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

4 Useful Micro-organisms
yeast carry out alcoholic fermentation in the presence of carbohydrates & the absence of O2 baking bread produces carbon dioxide to raise the dough brewing beer / making wine fermentation to produce alcohol

5 Useful Micro-organisms
nitrogen-fixing bacteria in leguminous plant [root nodules] carry out nitrogen fixation which changes N2 gas from the air to nitrogenous compounds for plants to produce protein

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

7 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. athlete’s foot , ringworm protozoa disease : e.g. malaria, sleeping sickness Dust Mite - multicellular athlete's foot

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

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

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

11 Antibiotics 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

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

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

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

15 Food Preservation 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

16 Food Preservation Refrigeration Freezing
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

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

18 Food Preservation Pickling Osmotic preservation
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

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

20 ~ END ~

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