A number of bacteria and protozoa are helpful in the digestion of food inside the stomach or small intestines of herbivores such as cows, goats and rabbits. Useful bacteria are also found in the human digestive system.
4. In sewage treatment plants, microorganisms such as anaerobic bacteria are used to decompose human faeces, producing carbon dioxide, methane gas and humus. Methane gas is used as fuel while humus is used as an organic fertilizer.
5. The decay process recycles important elements such as carbon and nitrogen found in dead tissues and makes them available for other organisms.
1. Bacteria and fungi are used in the production of antibiotics. For example, penicillin is produced by fungi and streptomycin is produced by bacteria.
2. Antibiotics are used to prevent the growth of other microorganisms and for the treatment of diseases such as gonorrhea, syphilis and tuberculosis.
3. Bacteria are also used in the production of vitamins and in genetic engineering to produce hormones such as insulin as well as growth hormones.
4. Dead bacteria and viruses are used to prepare vaccines for disease such as tuberculosis, chickenpox, smallpox and measles.
1. Nitrogen is an important element for the synthesis of proteins in plants and animals. Atmospheric nitrogen cannot be used directly by both plants and animals.
2. Plants can only absorb nitrogen in the form of ions alike ammonium ions (NH+4), nitrites (NO2-) and nitrates (NO3-) from the soil.
3. Bacteria and fungi are used in agriculture to increase the amount of nitrogen elements in the soil and to recycle nitrogen as shown in the nitrogen cycle.
(a) Nitrogen-flixing bacteria are found in the root nodules of legume plants such as groundnuts. These bacteria change atmospheric nitrogen into nitrates. The nitrates are then absorbed by plants and used for making plant proteins.
(b) The plants are then eaten by animals and the plant proteins are changed into animal proteins. When both the plants and animals die, decaying bacteria and fungi carry out the decay process. The proteins are changed into ammonium compounds.
(c) The ammonium compounds are then changed into nitrites and finally into nitrates by nitrifying bacteria.
(d) The nitrates in the soil can be converted back into nitrogen gas by denitrifying bacteria.
4. Microorganisms are used in biological control to kill pests. For example, Bacillus thuringiensis is used to kill fly larvae and caterpillars while the Myxomatosis virus is used to control the population of wild rabbits in Australia.
1. Microorganisms such as yeast and bacteria are used in food processing industries.
2. Making bread
Yeast is added to bread dough which contains carbohydrates such as starch and glucose. Yeast cells carry out anaerobic respiration which releases carbon dioxide gas. This causes the dough to rise, producing bread.
3. Producing alcohol
Beer, wine and brandy are produced by the fermentation process using yeast.
Yeast is added to fruits (example: grapes) or cereals (examples: malt, barley). The zymase enzyme which is produced by yeast cells acts on the glucose found in these fruits and cereals. Ethanol, carbon dioxide and energy are produced as shown in the equation below:
4. Making yogurt
The fermentation of milk by bacteria at 46C produces yogurt which
is then chilled at 5C. The bacteria acts on the sugar in milk
(lactose), changing it into lactic acid which then curdles the milk
protein. The acid gives a sour taste to yogurt.
5. Making cheese
Bacteria act on the sugar in milk (lactose) to produce lactic acid which then coagulates the milk protein, forming cheese.
6. Making vinegar
Bacteria act on ethanol and change it into acetic acid (vinegar) by means of anaerobic respiration:
7. Making Soya sauce
Bacteria and fungi are mixed with wheat and soya beans. This mixture is then incubated for a certain period, producing soya sauce.
8. Producing beta-carotene, iodine and jelly
Seaweed is a source of food for humans and animals. Useful substances such as iodine and beta-carotene are obtained from algae. Iodine helps to prevent goiter while beta-carotene is helpful in preventing cancer.
9. Making leather products
Decomposing bacteria are used to separate the hard skin from the soft tissues of an animal’s hide to produce leather.