Microbiology and Biotechnology

Bacteria, fungi and viruses are often called micro-organisms. All bacteria and viruses are too small to be seen with the unaided eye and a microscope is needed to see them – some viruses are invisible under a low powered microscope and need to be magnified much greater to become visible.

Some fungi are also so small as to be only visible under the microscope but many fungi are very large, some as big as footballs. Microbiology is the name used for the study micro-organisms;

Micro-organisms are found in all types of habitat in the air, water, soil, on the surface and inside other living organisms, inside cells and even in solid rock to a depth of over 1,600 metres.

A disease-causing organism is called a pathogen. Our major pathogens are bacteria and viruses.

Some bacterial diseases: pneumonia, whooping cough, tuberculosis and leprosy.

Some viral diseases: common cold, Flu, AIDS, Hepatitis.

Note: most bacteria are harmless to us – only a minor number cause us problems.


1. Bacteria are single-celled organisms about 1,000 times smaller than a human cell.

2. The bacterium cell does not have a nucleus but their genes are carried on a loop of DNA in the cytoplasm.

3. Bacteria are in all types of habitat. Life on earth depends on bacteria.

4. Most bacteria are feed on dead organic matter; only a relatively few types of bacteria cause us harm.

5. Some bacteria cause diseases of plants, animals and humans; pathogenic bacteria.

6. Bacterial reproduction is quick and asexual; they double their numbers in good conditions every 20 mins.

7. Some human diseases caused by bacteria: tuberculosis (TB), food poisoning, pneumonia, cholera, septic sore throat, leprosy.


1. Often described as ‘plant-like’ but without chlorophyll.

2. All are consumers – fungi cannot make their own food, they cannot photosynthesise; most are decomposers and some cause disease.

3. Fungi vary from microscopic multicellular types like yeast to very large ‘multicellular’ types like giant puff balls and shelf fungi.

4. The cells of fungi have nuclei that contain their genes.

5. Some fungi cause disease of plants, animals and humans.

5. Some human diseases caused by fungi: athlete’s foot, ringworm, poisoning, breathing disorders, thrush.


1. Many biologists do not classify viruses as living organisms. (they cannot reproduce on their own)

2. Viruses are not made of cells they appear rather simple – just a piece of genetic material carrying a few genes surrounded by a protective coat of protein.

3. Viruses are extremely small; many cannot even be seen with a light microscope.

4. Viruses cannot reproduce by themselves – they need to hijack living cells to make new viruses.

5. All viruses cause disease – they attack and destroy the cells of bacteria, fungi, plants, animals and humans.

6. Some diseases caused by viruses: common cold, flu, measles, AIDS, viral hepatitis, winter vomiting bug.

MandPractivity 10 Investigate the Presence of Micro-organisms in Air and Soil

1. You have three sterile nutrient agar plates.

2. One plate is not opened; the lid is sealed tight to the base with parafilm – this is the control.

3. A second plate is opened and left exposed to air for 5 minutes then sealed. Write ‘air’ on the base.

4. The third plate is opened slightly and a small amount of soil is sprinkled onto the agar from a sterile spoon. The lid is replaced and sealed as before and ‘soil’ is written on the base.

5. All three plates are left upside down and incubate in an incubator at 30°C for 3 days

Incubating upside down is to prevent condensation on the lid and so the surface of the agar can be seen. Results Plate 1: the control – it must be clear without any growth of micro-organisms; if micro-organisms are growing on it then the investigation cannot continue and must be begun again.

Plates 2 and 3: fluffy growths are probably fungus; round shiny pimples are colonies of bacteria. The growths are micro-organisms that were present in the air and soil.

7. Flood all plates with sterilising fluid to kill the micro-organisms before disposal of the agar and the plates.


Biotechnology is the use of living organisms, their organelles or enzymes for the industrial production of substances of commercial and/or medical value. There are about 2,000 biotechnology companies; Bacteria and yeast are the major organisms used in biotechnology. Modern genetics has allowed the production of genetically modified bacteria and yeast to produce human proteins of medical value on a large scale.

Biotechnology is applied biological science as the industrial process was developed using the knowledge gained about micro-organisms through scientific study.

Uses of Biotechnology in Industry

1. Use of yeast in brewing to produce alcohol in beer.

2. Production of food additives e.g. amino acids.

3. Enzymes for washing powders.

4. Production of citric acid for the soft-drinks industry.

Uses of Biotechnology in Medicine

1. Bacteria and fungi are ‘pharmed’ to produce antibiotics.

2. Bacteria and fungi are grown to produce vitamins.

3. Many medically important proteins are produced by biotechnology:

(a) Hormones e.g. insulin, growth hormone, thyroxine, erythropoietin.

(b) Blood clotting factors.

(c) Antibodies to protect against infection by specific pathogens.

(d) Digestive enzymes – preparation of predigested foods for patients in hospitals.