Biology SS 1 Week 4
Topic: Micro-Organisms in our Environment
Micro-organisms found in Air and Water
Air: The air harbour micro-organisms like fungi (Rhizopus, Yeast, Mucor, Aspergillus and Penicillium spores); bacteria like Mycobaterium spp, micrococci, sarcina and finally viruses like Rhino virus (which causes common cold), pox virus, measle virus, etc.
Water: Bacteria like Salmonela, Mycobacteria, Escherichia Proteus, Pseudomonas are known to live in water. Others are phytoplanktons, blue-green algae, fungi like Aspergillus, Rhizopus, moulds, oscillatoria, spirogyra and ulothrix. The protozoa include Amoeba and Paramecium
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. Micro-organisms are known to live naturally in our bodies. They are referred to as body flora. Some live inside our bodies e.g. the colon or intestine and are called coliforms e.g. Escherichia coli, Klebsiella, Salmonella and Proteus
Others live inside our mouth, nose, ear, throat etc., examples are streptococcus spp, staphylococcus spp, haemophilus, yeast cells. Those that live on the skin include streptococcus, pseudomonas and staphylococcus.
Some of these micro-organisms are harmless and are known to protect the body; but when they are given the chance, they can cause disease. Example is the Coliforms which can produce vitamin K as well as cellulose especially in ruminants where it breaks down cellulose.
Ways and Places Through which Micro-organisms Enter the Body
Micro-organisms enter the body through the following ways:
- The mouth: Micro-organisms will pass through the mouth when we eat contaminated food or drink contaminated water
- The nose: Micro-organisms will pass through the nose when we breathe in contaminated air
- The skin: Due to the presence of wounds, micro-organisms can enter the body through them
- The anus: Micro-organisms can enter into the body through the anus since it is an opening
- 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
- Blood contact: Micro-organisms can enter the body through blood contact, e.g. infection of vaccines or drugs and blood transfusion
- Birth: Micro-organisms can also enter the body during child birth via umbilicus or vaginal canal
- Sexual contact: Micro-organisms can enter the body through sexual contacts, e.g. sexually transmitted disease (STDs) like gonorrhea, syphilis, AIDS, etc.
Carriers of Micro-Organisms
Carriers are agents which are capable of transferring or carrying micro-organisms from one place to another. Non-living 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, hairy bodies, etc. to carry micro-organisms. Therefore, micro-organisms can be located in the mouth parts, legs, abdomen, wings and hairy bodies of insects.
Important living (animal) carriers of micro-organisms, the micro-organisms they carry and the diseases they cause
| Vector or Carrier | Micro-organism | Disease caused |
| Anopheles (female) mosquito | Plasmodium | Malaria fever |
| Tse-tse fly | Trypanosome | Sleeping sickness |
| Housefly | Vibro cholerae | Cholera and typhoid fever |
| Rat fles / body louse | Rickettsia | Typhus |
| Aedes mosquito | Virus | Yellow fever and Dengue fever |
| Rat fleas | Bacterium | Plague |
