- 1 What are Friendly Micro Organisms and Their Uses?
The Biology Topics of ecology involves studying the relationships between living organisms and their environment.
What are Friendly Micro Organisms and Their Uses?
Initially it was thought that all the micro-organisms are harmful and cause diseases. Later on scientists discovered that only a handful of micro-organisms are harmful and cause diseases. Most of the micro-organisms are harmless and some of the micro-organisms are even beneficial to us (or useful to us). Micro-organisms play an important role in our lives. We will now describe the beneficial effects and harmful effects of micro-organisms in detail, one by one.
Friendly Micro Organisms (Or Useful Micro Organisms)
Micro-organisms are used for various purposes by human beings as well as in nature. Some of the beneficial effects (or uses) of micro-organisms are as follows :
- Micro-organisms are utilised in the making of curd, bread and cake.
- Micro-organisms are used in the production of alcohol, wine and acetic acid (vinegar).
- Micro-organisms are used in the preparation of medicines (or drugs) called antibiotics.
- Micro-organisms are used in agriculture to increase the fertility of soil by fixing atmospheric nitrogen gas (to form nitrogen compounds).
- Micro-organisms clean up the environment by decomposing the organic matter of dead plants, dead animals and animal wastes into harmless and useful simple substances. In this way, micro-organisms help in the recycling of materials in nature.
We will now study the beneficial effects (or uses) of micro-organisms in somewhat detail.
1. Making of Curd
Milk is turned into curd by bacteria. In order to make curd, a little pre-made curd is added to warm milk and set aside for some time. Curd contains several micro-organisms including Lactobacillus bacterium (Plural of Lactobacillus is Lactobacilli). Lactobacilli bacteria promote the formation of curd from milk. When a little of pre-made curd is added to warm milk, then Lactobacilli bacteria present in curd multiply in milk and convert it into curd.
This happens as follows : Milk contains a sugar called lactose. Lactobacilli bacteria convert the lactose sugar into lactic acid. This lactic acid then converts milk into curd. We can now say that the micro-organism utilised in making curd from milk is bacterium (or bacteria). The name of this bacterium is Lactobacillus. An important ingredient of idlis and bhaturas is curd. Curd is added in making idlis and bhaturas to make them soft and spongy. Bacteria are also involved in the making of cheese, pickles, and many other food items.
2. Making of Bread
Yeast is used in the baking industry for making bread.
When yeast is mixed in dough for making bread, the yeast reproduces rapidly and gives out carbon dioxide gas during respiration. The bubbles of carbon dioxide gas fill the dough and increase its volume. This makes the bread ‘rise’. The holes in the bread are due to the bubbles of carbon dioxide given off during the baking process (see Figure).
This makes the bread light, soft and spongy. For the same reason, yeast is also used in making cakes and pastries. We can perform an activity to demonstrate the action of yeast in the making of bread as follows.
Take half a kilogram of white flour (maida), add some sugar and mix with warm water. Then add a small amount of yeast powder and knead the mixture of white flour, sugar, yeast powder and water to make a soft dough [see Figure (a)], Keep this dough aside for about 2 hours.
We will find that the volume of dough has increased [see Figure (b)]. We say that the dough rises. From this discussion we conclude that yeast is the micro-organism used in making bread, cakes and pastries. Yeast is a fungus.
3. Commercial Use of Micro-Organisms
Micro-organisms are used for the large scale production of alcohol and acetic acid (vinegar). Yeast is the micro-organism which is used for the large scale production of alcohol. This alcohol is then used in making wine, beer and whisky as well as industrial spirit. So, we can now say that yeast is used to produce alcoholic drinks (such as wine, beer, whisky, etc.) and industrial spirit.
Yeast is capable of converting sugar into alcohol (and carbon dioxide). The sugar for making alcohol comes from substances such as cane juice and fruit juices, or from substances such as barley, maize, rice, etc. (that contain starch which gets converted into sugar). The process of conversion of sugar into alcohol by the action of yeast is called fermentation.
Fermentation was discovered by Louis Pasteur in 1857. In order to make alcohol, yeast is grown on natural sugars present in grains like barley, maize, rice, cane juice and fruit juices, etc. Yeast converts sugar into alcohol. This alcohol is then used for various purposes. We can carry out the process of alcoholic fermentation in the laboratory as follows.
Take a 500 mL beaker and fill it three-fourths with water. Dissolve 2 or 3 teaspoonfuls of sugar in it. Add half a teaspoonful of yeast powder to the sugar solution. Cover the beaker and allow the mixture of sugar solution and yeast powder to stand in a warm place for 4 to 5 hours. Now, smell the solution.
We will get a characteristic pleasant smell coming from the beaker. This is the smell of alcohol (because sugar has been converted into alcohol by yeast). Now taste the solution from the beaker. We will get a ‘burning taste’. This burning taste is due to the formation of alcohol.
A dilute solution of acetic acid is called vinegar. Bacteria can turn alcohol into acetic acid (or vinegar). In order to produce acetic acid (or vinegar) on a large scale, first alcohol is made by using yeast. The Acetobacter bacteria are then added to alcohol and air is bubbled through it. In the presence of oxygen (of air), Acetobacter bacteria convert alcohol into acetic acid (or vinegar).
4. Medicinal Use of Micro-Organisms
A medicine which stops the growth of, or kills the disease-causing micro-organisms is called an antibiotic. The source of antibiotic medicines are micro-organisms. The antibiotics are manufactured by growing specific micro-organisms (and used to cure a number of diseases). These days, a large number of antibiotics are being produced from micro-organisms such as fungi and bacteria.
Some of the common antibiotics which are made from fungi and bacteria are : Penicillin, Streptomycein, Erythromycein and Tetracycline. Nowadays, many antibiotics are also being made synthetically. Many different antibiotics are now available to treat a wide variety of diseases caused by pathogenic micro-organisms. Antibiotics kill the disease-causing micro-organisms but usually do not damage human body cells.
The first antibiotic ‘penicillin was discovered by chance and extracted from the tiny fungus (a mould) called ‘Penicillium’. This happened as follows : In 1929, Alexander Fleming was cultivating a culture of disease- causing bacteria. Suddenly he found the spores of a little green ‘fungus’ in one of his culture plates.
He noticed that the presence of tiny green fungus stopped the growth of disease-causing bacteria. In fact, it also killed many of the disease-causing bacteria. From this fungus (or mould) called ‘Penicillium’, the antibiotic penicillin was made. Thus, penicillin is an antibiotic medicine which is made from the fungus ‘Penicillium’. Penicillin controls bacterial and fungal infections.
Antibiotics are used to treat many diseases in humans. Whenever we fall ill, the doctor may give us some antibiotic tablets, capsules or injections (such as penicillin) (see Figure).
Antibiotics are very effective in curing diseases caused by micro-organisms such as bacteria and fungi. Antibiotics are, however, not effective against diseases caused by viruses. For example, antibiotics cannot be used to cure diseases like ‘common cold’, ‘flu’, and ‘viral fever’ because these are caused by viruses. Some of the precautions to be observed in the use of antibiotics are as follows
- Antibiotics should be taken only on the advice of a qualified doctor.
- A person must complete the ‘full course’ of antibiotics prescribed by the doctor.
- The antibiotics should be taken in proper doses as advised by the doctor. If a person takes antibiotics in wrong doses (or when not needed), it may make the antibiotics less effective when the person might need it in future.
- Antibiotics should not be taken unnecessarily. Antibiotics taken unnecessarily may kill the useful bacteria in the body and harm us.
Antibiotics can be used to treat many diseases in animals. Antibiotics are even mixed with the feed of live stock (cattle like cows, buffaloes, etc.) and poultry birds to control microbial diseases in animals. Antibiotics are also used to control many plant diseases.
We have just studied that micro-organisms are used to make medicines called antibiotics which can cure many diseases in human beings, animals and plants. Mirco-organisms are also used to make vaccines. A vaccine is a special kind of preparation (or medicine) which provides immunity (or protection) against a particular disease.
Vaccines are given to healthy persons so that they may not get certain diseases throughout their life (even if they are exposed to the pathogens of these diseases later on in life). These days vaccines are made on a large scale from micro-organisms to protect human beings and other animals from several diseases. A vaccine works as follows :
A vaccine contains the dead or weakened but alive micro-organisms of a disease (which are harmless and do not actually give a disease). When the vaccine containing dead or alive micro-organisms is introduced into the body of a healthy person orally (by mouth) or by injection, the body of that person responds by producing some substances called ‘antibodies’ in its blood.
These antibodies kill any ‘alive’ disease-causing micro-organisms present in the vaccine. Some of the antibodies remain in the blood of the person for a very long time and fight against the same micro-organisms and kill them if they happen to enter the body naturally at a later date (when the person is exposed to disease). So, due to the presence of antibodies in the blood, a person remains protected from that particular disease. Thus, a vaccine develops the immunity from a disease.
A number of diseases can be prevented by vaccination. Vaccination is the process of giving a vaccine orally (by mouth) or by injection which provides protection against a particular disease. For keeping good health, we must prevent the diseases by vaccination at the proper time.
Since children are more susceptible to diseases, so all the children should be vaccinated at proper ages to provide them immunity from certain diseases. The diseases which can be prevented by vaccination of children at proper age are: Polio, Smallpox, Cholera, Typhoid, Hepatitis, Tuberculosis (TB), Tetanus, Measles, Rabies, Diphtheria and Pertussis (Whooping cough).
To develop the fighting capability in the body to a disease in called ‘immunisation. After getting vaccinated, the child becomes ‘immune to a particular disease. This means that the child becomes protected against that disease. He will never get that disease. Edward Jenner discovered the vaccine for smallpox in 1798.
A worldwide campaign against smallpox has finally led to its eradication from most parts of the world. Under the National Health Programme in our country the vaccines for several diseases are given free of cost at all the Government Health Centres. Polio disease is prevented by giving Oral Polio Vaccine (OPV) (see Figure).
Many times we see advertisements on TV and in newspapers to protect the children from polio under the Pulse Polio Programme by giving them polio drops. The polio drops given to children are actually a vaccine.
5. Increasing Soil Fertility
Some of the micro-organisms present in the soil can fix nitrogen gas from the atmosphere to form nitrogen compounds. These nitrogen compounds mix with the soil and increase the fertility of soil. For example, some bacteria and blue-green algae are able to ‘fix’ nitrogen gas from the atmosphere to enrich the soil with nitrogen compounds and increase its fertility. The nitrogen-fixing bacteria and blue-green algae are called biological nitrogen fixers. The nitrogen-fixing blue-green algae are shown in Figure.
Since blue-green algae store in them nitrogen compounds made by nitrogen-fixation, they are used as fertiliser in agriculture. The addition of blue-green algae to barren fields increases the nitrogen content of the soil and makes it fertile. Rhizobium bacteria present in the root nodules of leguminous plants (like peas, beans, etc.) also fix atmospheric nitrogen and increase soil fertility.
6. Cleaning the Environment
Some micro-organisms (like certain bacteria and fungi) decompose the organic matter present in dead plants, dead animals and animal wastes, and convert them into simple substances which mix up with the soil. These simple substances contain plant nutrients which are again used by new plants for their growth.
Since micro-organisms decompose the harmful and smelly dead remains of plants and animals, and animal wastes (like faeces, dung, urine, etc.) into harmless materials, they clean the environment. If, however, there were no micro-organisms (called decomposers) in the soil, then the dead plants, dead animals and animal wastes would keep/on piling up in the environment and make it dirty.
In addition to cleaning the environment, the micro-organisms also help in recycling the nutrients (present in dead plants, dead animals and animal wastes) in nature which can then be used as food by green plants. If there were no micro-organisms (called decomposers), then the nutrients present in dead plants, dead animals and animal wastes would never be released for use by new plants.
We will now describe on activity to show that some micro-organisms decompose waste plant materials and convert them into useful manure. Take two flower pots and mark them A and B. Fill each flower pot half with soil. Take some plant wastes such as fruit and vegetable peels, fallen leaves, etc., and bury them in soil in pot A. Bury a polythene bag, an empty glass bottle and a broken plastic toy in the soil in pot B.
Keep both the pots aside for 3 to 4 weeks. If we now observe the pot A, we will find that the plant wastes buried in it have been decomposed. The plant wastes (fruit and vegetable peels, fallen leaves, etc.) have been decomposed by the action of micro-organisms present in the soil and converted into manure.This manure contains the nutrients released from plant wastes. These nutrients can be used for growing new plants.
If, however, we look at the pot B, we will find that the polythene bag, glass bottle, and plastic toy did not get decomposed, and remained as such. This is because the micro-organims present in soil are not able to decompose polythene bag, glass and plastic and convert them into manure. The micro-organisms present in soil can decompose only the organic matter present in dead plants, dead animals and animal wastes, etc.