Microorganisms, Friend and Foe

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Microorganisms: Friend and Foe

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There exist around us, living organisms, which can normally not be seen with an unaided eye. These are called micro-organisms or Microbes. Some micro-organisms like fungi grow in colonies and can be seen with an unaided eye, but most micro-organisms can only be seen under a magnifying glass or a microscope. Micro-organisms are classified into four major groups; Bacteria; Fungi; Protozoa; and Algae. What are Micro-organisms?

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Bacteria Spiral bacteria Rod-shaped bacteria Algae Chlamydomonas Spirogyra Protozoa Amoeba Paramecium Fungi Bread Mould Penicillium Aspergillus

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Viruses are also microscopic. They however reproduce only inside the cells of a 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. Virus

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Where do micro-organisms live and how do they help us? Micro-organisms may be single-celled like bacteria, some algae and some protozoa, or multicellar , 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. 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. In agriculture they are used to increase soil fertility by fixing nitrogen. (contd. on Page 6)

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In agriculture they are used to increase soil fertility by fixing nitrogen. Milk is turned into curd by bacteria. 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. An important ingredient of bhaturas and rava (sooji) idlis is curd. Where do micro-organisms live and how do they help us?

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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. The process of conversion of sugar into alcohol is known as fermentation. Louis Pasteur discovered fermentation in 1857.

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Whenever you fall ill the doctor may give you some antibiotic tablets, capsules or injections such as of penicillin. The source of these medicines is 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. These medicines kill or stop the growth of the disease-causing microorganisms. 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. Medicinal Use of Microorganisms

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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 you 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. Precautions while Administering Antibiotics

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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. Penicillin

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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. Children are given injections to protect themselves against several diseases. Necessary vaccines are available in hospitals. Vaccinations are given to children for protection against polio under Pulse Polio Program. Polio drops given to children are actually a vaccine. This is called Oral vaccination. These days vaccines are made on a large scale from microorganisms to protect humans and other animals from several diseases. Vaccine

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Smallpox is an infectious disease unique to humans, caused by either of two virus variants, Variola major and Variola minor . Smallpox is believed to have emerged in human populations about 10,000 BC. The disease killed an estimated 4,00,000 Europeans each year during the 18th century A worldwide campaign against smallpox has finally led to its eradication from most parts of the world. The vaccine for smallpox was discovered by Edward Jenner in 1798. Small Pox

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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. Increasing Soil Fertility

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You often see large amounts of dead organic matter in the form of decaying plants and sometimes dead animals on the ground. You 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. Cleaning the Environment

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Microorganisms are harmful in many ways. Some of the microorganisms cause diseases in human beings, plants and animals. Such disease-causing microorganisms are called pathogens. Pathogens enter our body through the air we breathe, the water we drink or the food we eat. They can also get transmitted by direct contact with an infected person or carried through an animal. Microbial diseases that can spread from an infected person to a healthy person through air, water, food or physical contact are called communicable diseases. Examples of such diseases include cholera, common cold, chicken pox and tuberculosis. When a person suffering from common cold sneezes, fine droplets of moisture carrying thousands of viruses are spread in the air. The virus may enter the body of a healthy person while breathing. (Contd. On page 16) Harmful Microorganisms

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There are some insects and animals which act as carriers of disease-causing microbes. Housefly is one such carrier. The flies sit on the garbage and animal excreta. Pathogens stick to their bodies. When these flies sit on uncovered food they may transfer the pathogens. Whoever eats the contaminated food is likely to get sick. So, it is advisable to always keep food covered. Avoid consuming uncovered items of food Examples of carriers are: the female Anopheles mosquito which carries the parasite of malaria; Female Aedes mosquito acts as carrier of dengue virus. Harmful Microorganisms All mosquitoes breed in water. Hence, one should not let water collect anywhere, in coolers, tyres , flower pot etc. By keeping the surroundings clean and dry we can prevent mosquitoes from breeding.

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Human Disease Causative Microorganisms Mode of Transmission Preventive Measures (General) Tuberculosis Measles Chicken Pox Polio Bacteria Virus Virus Virus Air Air Air/Contact Air/Water Keep the patient in complete isolation. Keep the personal belongings of the patient away from those of others. Vaccinations to be given at suitable age Cholera Typhoid Bacteria Bacteria Water/Food Water Maintain personal hygiene and good sanitary habits. Consume properly cooked food and boiled drinking water. Vaccination Hepatitis A Virus Water Drink boiled drinking water. Vaccination. Malaria Protozoa Mosquito Use mosquito net and repellents. Spray insecticides and control breeding of mosquitoes by not allowing water to collect in the surroundings. Some Common Human Diseases caused by Microorganisms

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Several microorganisms not only cause diseases in humans and plants, but also in other animals. For example, anthrax is a dangerous human and cattle disease caused by a bacterium. Foot and mouth disease of cattle is caused by a virus. Robert Köch (1876) discovered the bacterium ( Bacillus anthracis) which causes anthrax disease. Disease-causing Microorganisms in Animals

Disease-causing Microorganism in Plants: 

Disease-causing Microorganism in Plants Several microorganisms cause diseases in plants like wheat, rice, potato, sugarcane, orange, apple and others. The diseases reduce the yield of crops. They can be controlled by the use of certain chemicals which kill the microbes.

Some Common Plant Diseases caused by Microorganisms: 

Some Common Plant Diseases caused by Microorganisms Plant Disease Microorganism Mode of Transmission Figure Citrus canker Bacteria Air Rust of wheat Fungi Air, seeds Yellow vein mosaic of bhindi (Okra) Virus Insect

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Food poisoning could be due to the consumption of food spoilt by some microorganisms. Microorganisms that grow in our food sometimes produce toxic substances. These make the food poisonous causing serious illness and even death. So, it is very important that we preserve food to prevent it from being spoilt. Food Poisoning

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Microorganisms spoil our food. Spoiled food emits bad smell and has a bad taste and changed colour. Salts and edible oils are the common chemicals generally used to check the growth of microorganisms. Therefore they are called preservatives. We add salt or acid preservatives to pickles to prevent the attack of microbes. Sodium benzoate and sodium metabisulphite are common preservatives. These are also used in jams and squashes to check their spoilage. Common salt has been used to preserve meat and fish for ages. Meat and fish are covered with dry salt to check the growth of bacteria. Salting is also used to preserve amla, raw mangoes, tamarind, etc. Jams, jellies and squashes are preserved by sugar. Sugar reduces the moisture content which inhibits the growth of bacteria which spoil food. Use of oil and vinegar prevents spoilage of pickles because bacteria cannot live in such an environment. Vegetables, fruits, fish and meat are often preserved by this method. These days dry fruits and even vegetables are sold in sealed air tight packets to prevent the attack of microbes. Food Preservation

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Boiling kills many microorganisms in milk. Low temperature inhibits the growth of microbes. Pasteurized milk can be consumed without boiling as it is free from harmful microbes. The milk is heated to about 70 Degrees Celsius for 15 to 30 seconds and then suddenly chilled and stored. By doing so, it prevents the growth of microbes. This process was discovered by Louis Pasteur. It is called pasteurization. Pasteurization

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Rhizobium bacteria is involved in the fixation of nitrogen in leguminous plants (pulses). Rhizobium lives in the root nodules of leguminous plants , such as beans and peas, with which it has a symbiotic relationship. Sometimes nitrogen gets fixed through the action of lightning. Nitrogen Fixation

Nitrogen Fixation: 

Nitrogen Fixation Our atmosphere has 78% nitrogen gas. Nitrogen is one of the essential constituents of all living organisms as part of proteins, chlorophyll, nucleic acids and vitamins. The atmospheric nitrogen cannot be taken directly by plants and animals. Certain bacteria and blue green algae present in the soil fix nitrogen from the atmosphere and convert into compounds of nitrogen. Once nitrogen is converted into these usable compounds, it can be utilized by plants from the soil through their root system. Nitrogen is then used for the synthesis of plant proteins and other compounds. Animals feeding on plants get these proteins and other nitrogen compounds. When plants and animals die, bacteria and fungi present in the soil convert the nitrogenous wastes into nitrogenous compounds to be used by plants again. Certain other bacteria convert some part of them to nitrogen gas which goes back into the atmosphere. As a result, the percentage of nitrogen in the atmosphere remains more or less constant.

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Nitrogen Cycle

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THE END By Vedant Chakravarthy 8 th ‘A’ K.V. I.I.Sc