MICRO-ORGANISMS AROUND US

Micro-organisms are tiny organisms which cannot be seen with the naked eye except with the aid of microscopes. The branch of biology which involves the study of organisms that are microscopic in sizes is called microbiology. Micro-organisms are found everywhere – in the soil, air, water, on our clothes, bodies, inside our bodies, etc. Some of the micro-organisms are beneficial, harmless or non-pathogenic while others cause diseases and are referred to as pathogenic and therefore harmful.

 

Groups of Micro-Organisms

All micro-organisms are grouped into the following:

1. Viruses.
2. Bacteria.
3. Protozoa.
4. Fungi.
5. Algae.

 

Viruses

Viruses are micro-organisms that are too tiny to be seen with ordinary microscopes except with the use of electron microscopes. Viruses are the simplest and the smallest micro-organisms which do not have a cell structure. Some are rod-like in shape while others are spherical. Each cell consists of a strand of nuclear protein. Virus may be grouped into DNA and RNA viruses. Some may be enveloped or without an envelope, i.e ., they are naked and can only reproduce inside a living cell. Examples of viruses are Adenovirus, Picornavirus, Togavirus and Coronavirus.

 

Bacteria

Bacteria are micro-organisms that can easily be seen with light microscope. They occur in clusters or colonies. A bacterium has slimy capsule, cell wall, a cell membrane, a dense cytoplasmic granules with no clear nucleus but has a nuclear material called DNA (Deoxyribose Nucleic Acid) which spreads through the cell.

 

Types of bacteria

Bacteria are grouped into two major types.

These are:

(a) Bacteria on the basis of the use of oxygen: Under this group, there exist three types. They are:

• Aerobic bacteria: These are bacteria that require oxygen for their respiration.
• Anaerobic bacteria: These are bacteria which do not require oxygen for their respiration.
• Falcultative bacteria: These are bacteria that can live under aerobic and anaerobic conditions.

 

(b) Bacteria on the basis of their shape: Under this group, there exist different shapes of bacteria. These are:

• Cocci: Cocci are circular in shape. Some may stick together to form a chain, hence they are called Streptococci, e.g. sore throat bacteria. Others which occur as bunch or in cluster form are called Staphylococci, e.g. boil bacteria. Yet some other bacteria called Diplococci stick together in pairs, e.g. bacteria that cause pneumonia. Again, when bacteria occur in group of four, they are known as tetrads.
• Bacilli: These bacteria are rod-like in shape. Some have flagella which they use for movement, e.g. bacteria that cause typhoid fever.
• Vibrio: Vibrio are curved in shape, just like a comma, e.g. cholera bacteria.
• Spirillae: Spirillae are spiral and twisted bacteria. Some are mobile, e.g. syphilis bacteria.

 

Protozoa: These micro-organisms are microscopic, free-living, unicellular animals, e.g. Amoeba and Paramecium. Some are parasites, e.g. trypanosomes which cause trypanosomiasis and plasmodium which causes malaria fever.

 

Fungi: Fungi are saprophytic or parasitic, non-green plants. The saprophytic fungi are beneficial while the parasitic fungi cause different types of diseases.

 

Algae: Algae are microscopic green plants with the majority mainly found in aquatic environment, e.g. Diatoms, Spirogyra, Volvox, Chlamydomonas, Oscillatoria and Nostoc.

 

CONCEPT OF CULTURING

Culturing simply involves the technique of growing micro-organisms in special media in the laboratory. It involves the making of sterile medium, innoculating, incubating and examining micro-organisms. By this means, microorganism characteristics such as colour, pattern of growth and appearance can be seen. Culture of micro-organisms can be grown from water, air, animals, plants and various parts of human body.

 

Preparation of Culture Solution

1. The culture solution called Agar is prepared under sterile conditions.
2. Then boil and pour it into sterile petri-dish.
3. Allow it to cool and set in the petri-dish.
4. A heat steriliser may be used to kill micro-organisms in the petri-dish.
5. The material is then introduced into the agar medium and covered immediately.
6. Place the petri-dish in a warm but dark compartment or an incubator.
7. Observe and record what you have seen for 2-3 days.

 

Instruments Required for the Preparation of Culture Solution

Major instruments required for the preparation of culture solution are:

• Microscope.
• Petri-dishes.
• Test tubes or test tube holder.
• Slides.
• Cover slips.
• Hand lens.
• Innoculating needles or loops.
• Innoculating chamber if available.

 

Precautions to be Taken During Preparation of Culture Solution

1. Wash hands with soap before and after the preparation of agar solution.
2. Open petri-dish only slightly and cover at once.
3. Close petri-dish firmly with adhesive tape.
4. Sick person should not be permitted to take part in culturing experiments.
5. Avoid talking, coughing, sneezing and touching of infected jelly.
6. Unused agar should be sterilised by washing with antiseptic soap and disinfectant, e.g. 40% folmadebyde. Heat can also be used to sterilise.
7. All instruments should also be sterilised before the beginning of culture solution preparation.

 

IDENTIFICATION OF MICRO-ORGANISMS

Micro-organisms can be identified in the air, pond water, river and stream by preparing a culture medium. Students are divided into working groups and each group is provided with culture medium.

The following procedures should be followed:

1. Five petri-dishes with culture medium are labelled K, L, M, N and O respectively.
2. Expose petri-dish K to air for about 10-15 minutes and then cover it.
3. Put in petri-dish L a few drops of pond water and cover it.
4. Put in petri-dish M a few drops of river water and cover it.
5. Put in petri-dish N a few drops of stream water and cover it.
6. Allow petri-dish O to serve as control, i.e ., do not introduce anything into it.
7. Leave all the petri-dishes in the laboratory for 3-4 days.
8. Observe all the petri-dishes for any development and note any difference in each of the petri-dishes.
9. Record the characteristics (colour, pattern of growth, appearance) of colonies of micro-organisms in each petri-dish.
10. The recorded observation is then followed by class discussion.

 

MICRO-ORGANISMS IN OUR BODIES AND FOOD

Micro-organisms are also found in or on our bodies such as mouth, in expired or exhaled air, in the dirt under the nails as well as in our food. Students should also carry out these experiments in the laboratory.

Students are divided into manageable groups. The following procedures should be used:

 

Experiment I

To Demonstrate the Presence of Micro-organisms in the Dirt Under the Finger Nails

1. Prepare a sterile medium.
2. Then use a sterile platinium or innoculating wire to pick some dirt under the nails.
3. Draw lightly in streaks on a sterile agar (culture medium) in a petri-dish labelled A.
4. Take every precaution to avoid contamination of the agar or culture medium.
5. Cover the petri-dish immediately after streaking.
6. Heat the platinium or innoculating wire to redness over a bunsen flame and allow to cool.
7. Then streak another sterile agar with the sterile plantinium wire, cover it and label it B, to serve as the control experiment.
8. Place petri-dishes A and B in a warm but dark cupboard or incubator and examine them daily.
9. It will be observed that clusters of bacteria culture (colonies) will appear on the line of the streak in petri-dish A and increase gradually in size.
10. There will be no growth on streaks in petri-dish B which shows that growth in petri-dish A is from bacteria introduced under the dirt in the finger nails.

 

Experiment II

To Demonstrate the Presence of Micro-organisms in the Teeth or Mouth

1. Prepare a sterile medium.
2. Use sterile cotton wool to clean the teeth very early in the morning, i.e ., before brushing with toothpaste or cleaning with chewing stick.
3. Then use platinium wire to collect extracts from cotton wool or chewing stick.
4. Draw lightly in streaks on a sterile agar (culture medium) in a petri-dish labelled C.
5. Take every precaution to avoid contamination of the agar or culture medium.
6. Cover the petri-dish immediately after streaking.
7. Heat the platinium or innoculating wire to redness over a bunsen flame and allow it to cool.
8. Then streak another sterile agar with the sterile platinium wire, cover it and label it petri-dish D to serve as the control experiment.
9. Place petri-dishes C and D in a warm, dark cupboard or incubator and examine them daily.
10. It will be observed that clusters of bacteria culture (colonies) will appear on the line of the streak in petri-dish C, and gradually increase in size.
11. There will be no growth on streaks made in petri-dish D which shows that growth in C is from bacteria introduced from the teeth or mouth.

 

Experiment III

To Demonstrate the Presence of Micro-organisms in Expired or Exhaled Air

1. Prepare a sterile medium.
2. Then blow air from the mouth into the medium (at least twice) , cover it immediately and label it petri-dish E.
3. Take every precaution to avoid contamination of the agar or culture medium.
4. In another sterile medium, do not blow air into it and it will serve as control experiment. This is labelled petri-dish F.
5. Place petri-dishes E and F in a warm dark cupboard or incubator and examine them daily.
6. It will be observed that clusters of macro-organisms culture (colonies) will appear on petri-dish E and gradually increase in size.
7. There will be no growth of microorganisms in petri-dish F which shows that the growth from petri-dish E is from bacteria introduced through exhaled air from the mouth.

 

Experiment IV

To Demonstrate the Presence of Micro-organisms in Food

1. Prepare a sterile medium.
2. Scoop some portion of the food (e.g. yam, cassava or eba, fufu, rice and beans) with innoculating wire.
3. Draw lightly in streaks on a sterile agar (culture medium) in a petri-dish labelled G.
4. Take every precaution to avoid contamination of the agar or culture medium.
5. Cover the petri-dish immediately after streaking.
6. Heat the innoculating wire to redness over a bunsen flame and allow it to cool.
7. Then streak another sterile agar with the sterile innoculating wire, cover it and label it petri-dish H to serve as control experiment.
8. Place petri-dishes G and H in a warm, dark cupboard or incubator and examine them daily.
9. It will be observed that clusters of micro-organisms culture (colonies) will appear on the line of the streak in petri-dish G and gradually increase in size.
10. There will be no growth on streaks in petri-dish H which shows that growth in G is from micro-organisms introduced from food.

 

Ways and Places Through which Micro-organisms Enter the Body

Micro-organisms enter the body through the following ways:

1. The mouth: Macro-organisms will pass through the mouth when we eat contaminated food or drink contaminated water.
2. The skin: Due to the presence of wounds, macro-organisms can enter the body through them.
3. The anus: Micro-organisms can enter into the body through the anus since it is an opening.
4. Animal bites: Carriers or vectors such as tse-tse flies and female anopheles mosquito which are carriers of parasites that cause sleeping sickness and malaria respectively can enter the body through bites.
5. Blood contact: Macro-organisms can enter the body through blood contact, e.g. infection of vaccines or drugs and blood transfusion.
6. Birth: Micro-organisms can also enter the body during child birth via umbilicus or vaginal canal.
7. Sexual contact: Micro-organisms can enter the body through sexual contacts, e.g. sexually transmitted disease (STDs) like gonorrhea, syphilis and AIDS.

 

CARRIERS OF MICRO-ORGANISMS

Carriers are agents which are capable of transferring or carrying microorganisms from one place to another. Nonliving agents that carry micro-organisms from place to place are air, water and food.

Animals are the living agents which transfer micro-organisms from one place to another. Animals that carry pathogenic micro-organisms are known as vectors.

Carriers use various parts of their bodies, e.g. legs, wings, mouth parts and hairy bodies to carry micro-organisms. Therefore, micro-organisms can be located in the mouth parts, legs, abdomen, wings and hairy bodies of insects.