We have seen several kinds of plants and animals. However, there are other living organisms around us which we cannot see with eyes alone. These are called microorganisms or microbes.
Microorganisms:
Water and soil are full of tiny organisms, though not all of them fall into the category of microbes. These microorganisms or microbes are so small in size that they cannot be seen with the unaided eye. Some of these, such as the fungus that grows on bread, can be seen with a magnifying glass. Others cannot be seen without the help of a microscope. That is why these are called microorganisms or microbes.
Microorganisms are classified into four major groups. These groups are
Viruses are also microscopic. They, however, reproduce only inside the cells of the host organism, which may be a bacterium, plant or animal. Common ailments like cold, influenza (flu) and most coughs are caused by viruses. Serious diseases like polio and chicken pox are also caused by viruses.
Diseases like dysentery and malaria are caused by protozoans whereas typhoid and tuberculosis (TB) are bacterial diseases.
Microorganisms are classified into four major groups. These groups are
- bacteria,
- fungi,
- protozoa and
- some algae.
Viruses are also microscopic. They, however, reproduce only inside the cells of the host organism, which may be a bacterium, plant or animal. Common ailments like cold, influenza (flu) and most coughs are caused by viruses. Serious diseases like polio and chicken pox are also caused by viruses.
Diseases like dysentery and malaria are caused by protozoans whereas typhoid and tuberculosis (TB) are bacterial diseases.
Where do Microorganisms Live?
- Microorganisms may be single-celled like bacteria, some algae and protozoa, or multi-cellular, such as algae and fungi.
- They can survive under all types of environment, ranging from ice cold climate to hot springs and deserts to marshy lands.
- They are also found inside the bodies of animals including humans.
- Some microorganisms grow on other organisms while others exist freely.
- Microorganisms like amoeba can live alone, while fungi and bacteria may live in colonies.
Microorganisms play an important role in our lives. Some of them are beneficial in many ways whereas some others are harmful and cause diseases.
Friendly Microorganisms
Microorganisms are used for various purposes.
- They are used in the preparation of curd, bread and cake.
- They are also used in cleaning up of the environment. For example, the organic wastes (vegetable peels, remains of animals, faeces, etc.) are broken down into harmless and usable substances by bacteria.
- Bacteria are also used in the preparation of medicines.
- In agriculture they are used to increase soil fertility by fixing nitrogen.
- Microorganisms have been used for the production of alcohol since ages.
Making of Curd and Bread:
Curd contains several microorganisms. Of these, the bacterium Lactobacillus promotes the formation of curd. It multiplies in milk and converts it into curd. Bacteria are also involved in the making of cheese, pickles and many other food items.
Yeast reproduces rapidly and produces carbon dioxide during respiration. Bubbles of the gas fill the dough and increase its volume. This is the basis of the use of yeast in the baking industry for making breads, pastries and cakes.
Commercial Use of Microorganisms:
Microorganisms are used for the large scale production of alcohol, wine and acetic acid (vinegar). Yeast is used for commercial production of alcohol and wine. For this purpose yeast is grown on natural sugars present in grains like barley, wheat, rice and crushed fruit juices, etc.
Sugar has been converted into alcohol by yeast.This process of conversion of sugar into alcohol is known as fermentation. Louis Pasteur discovered fermentation in 1857.
Medicinal Use of Microorganisms
Whenever we fall ill the doctor may gives us some antibiotic tablets, capsules or injections such as of penicillin. The source of these medicines is microorganisms. These medicines kill or stop the growth of the disease-causing microorganisms.Such medicines are called antibiotics.
These days a number of antibiotics are being produced from bacteria and fungi. Streptomycin, tetracycline and erythromycin are some of the commonly known antibiotics which are made from fungi and bacteria.
The antibiotics are manufactured by growing specific microorganisms and are used to cure a variety of diseases. Antibiotics are even mixed with the feed of livestock and poultry to check microbial infection in animals. They are also used to control many plant diseases.
Notes:- In 1929, Alexander Fleming was working on a culture of disease causing bacteria. Suddenly he found the spores of a little green mould in one of his culture plates. He observed that the presence of mould prevented the growth of bacteria. In fact, it also killed many of these bacteria. From this the mould penicillin was prepared.
It is important to remember that antibiotics should be taken only on the advice of a qualified doctor. Also you must finish the course prescribed by the doctor. If you take antibiotics when not needed or in wrong doses, it may make the drug less effective when we might need it in future.
Also antibiotics taken unnecessarily may kill the beneficial bacteria in the body. Antibiotics, however, are not effective against cold and flu as these are caused by viruses.
Vaccine
When a disease-carrying microbe enters our body, the body produces antibodies to fight the invader. The body also remembers how to fight the microbe if it enters again. So, if dead or weakened microbes are introduced in a healthy body, the body fights and kills them by producing suitable antibodies.
The antibodies remain in the body and we are protected from the disease causing microbes. This is how a vaccine works. Several diseases, including cholera, tuberculosis, smallpox and hepatitis can be prevented by vaccination. Edward Jenner discovered the vaccine for smallpox in 1798.
The antibodies remain in the body and we are protected from the disease causing microbes. This is how a vaccine works. Several diseases, including cholera, tuberculosis, smallpox and hepatitis can be prevented by vaccination. Edward Jenner discovered the vaccine for smallpox in 1798.
Polio drops given to children are actually a vaccine. A worldwide campaign against smallpox has finally led to its eradication from most parts of the world.
Increasing Soil Fertility : Some bacteria and blue green algae are able to fix nitrogen from the atmosphere to enrich soil with nitrogen and increase its fertility. These microbes are commonly called biological nitrogen fixers.
Cleaning the Environment
The plant waste has been converted into manure by the action of microbes. The nutrients released in the process could be used by the plants again. We often see large amounts of dead organic matter in the form of decaying plants and sometimes dead animals on the ground. We find that they disappear after some time. This is because the microorganisms decompose dead organic waste of plants and animals converting them into simple substances. These substances are again used by other plants and animals.
Thus, microorganisms can be used to degrade the harmful and smelly substances and thereby clean up the environment.
MICRO ORGANISMS - FRIEND AND FOE - PART II
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