Microorganisms: Friend and Foe
Science Class Eight
Summary
(1) Microorganisms:
Living organisms which cannot be seen without using microscope, are called microogranisms. For example bacteria, fungi, protozoa, etc.
(2) Microbes:
Microorganisms are known as Microbes also.
(3) Microbiology:
The study of microorganisms is known as Microbiology.
(4)Classification of Microorganism
According to some special characteristics, microorganisms or microbes are classified mainly into four groups. These four groups are (1) bacteria, (2) fungi, (3)protozoa and (4)some algae. Apart from these viruses are also microscopic living organisms.
(a) Bacteria
Bacteria are single cell organisms. Some bacteria are useful for us while some are harmful and cause of many diseases.
Shape of Bacteria
Bacteria can be of many shapes, they can be rod shaped, round shape, and spiral shaped. Bacteria were one of the first life forms appeared on the earth. Staphylococcus, Vibrio cholera, Brucelleae, Caryophanaceae, etc. are name of some bacteria.
Many diseases, such as typhoid, tuberculosis, etc. are caused by bacteria and consequently are called bacterial diseases.
The study of bacteria is known as Bacteriology, which is a branch of Microbiology.
(b) Fungi
Fungi can be single cellular and multicellular both. Mushroom, yeast, bread mould, etc. are examples of some fungi.
Reference: By Archenzo - Own work, CC BY-SA 3.0, Link
Mode of Nutrition in Fungi
Fungi are heterotrophs, which reproduce and get their nutrition on decomposing organisms. Fungi are called natural decomposer. Fungi get their food by secreting digestive juice of over decaying materials, this digestive juice dissolve the molecules of decaying organism and then fungi absorb the dissolve molecules as their food.
(c) Protozoa
Protozoa are single cellular organisms. Amoeba, paramecium, etc. are some examplea of protozoa. Protozoa may live freely or as a parasite. Dysentery, malaria, etc. are some diseases caused because of protozoa.
Reference: Frank Fox [CC BY-SA 3.0 de], via Wikimedia Commons
(d) Algae
Algae can be seen easily in stagnant water. Algae are considered as plant. Algae may be green and brown or reddish in color. Seaweeds are largest and most complex marine algae. Because of presence of chloroplast, algae perform photoshynthesis. Charophyta, Spirogyra, stoneworts, etc. are examples of some algae.
(e) Virus
Virus are parasites because they feed on other living organisms. Virus multiplies and replicates in the cells of other living organism only. Virus can infect almost all types of life forms including bacteria also. Virus is cause of many diseases. Small pox, Measles, Hepatitis B, AIDS, Common cold, Polio, etc. are diseases caused due to virus. Virus can be spread by air and by animals.
Reference: By Photo Credit: Cynthia GoldsmithContent Providers(s): CDC/ Dr. Terrence Tumpey/ Cynthia Goldsmith - This media comes from the Centers for Disease Control and Prevention's Public Health Image Library (PHIL), with identification number #8243.Note: Not all PHIL images are public domain; be sure to check copyright status and credit authors and content providers., Public Domain, Link
(5) Where do Microorganisms Live?
Microorganism is found everywhere and can survive in almost every condition. Microorganisms can be found ranging from ice cold climate to hot spring and desert to marshy lands. Microorganisms are found even inside the bodies of animals and can grow over the other organisms. Many microorganisms exist freely in the environment. Many microorganisms, such as amoeba live alone while many, such as fungi and bacteria may live in colonies.
(6) Microorganims and Us
Microorganisms play very important role in our life. It can be said that without microorganisms, our life is not possible as they play very important role in our life.
Some of the microorganisms are very useful to us while many are harmful for us. This means some microorganims are our friend while many are our enemy.
(7) Friendly Microorganisms
Many microorganisms are very much useful to us, means they are our friend.
Yeast, which is a type of fungi, is used to make bread and cake. Yeast is used in the production of alcohol right from ancient time. Fermentation takes place when yeast is put in the fruit juice. Yeast makes doe prepared for making of bread soft.
Microorganisms are used to clean environment. Microorganism decomposes organic waste such as vegetable peel, remains of animals, etc and convert them into harmless substances.
Microorganisms are used in making of medicines and enhance soil fertility by fixing of nitrogen.
(8) Bacteria in Making of Curd
To covert milk into curd, a small amount of curd is mixed into milk. One of the microorganisms called lactobacillus found in curd multiplies in milk and coverts the milk into curd.
(9) Commercial Use of Microorganisms
Microorganisms is used for the commercial production of alcohol, wine, and vinegar, etc. Yeast is used for the commercial production of alcohol and wine. Yeast converts sugar present in barley, wheat, rice, and fruit juices, into alcohol. For production of alcohol and wine fruit juice is left for many days at hot place after introducing small amount of yeast in them. This yeast replicates and converts sugar present in fruit juice into alcohol. However, fruit juice can be converted into alcohol and wine even without introducing yeast in them.
(10) Fermentation
The process conversion of fruit juice into alcohol by microorganisms is called Fermentation.
(a) Discovery of Fermentation
Louis Pasteur, who was a French Scientist, discovered fermentation in the year of 1857. Louis Pasteur discovered the process to preserve milk also. In his honour the process to preserver milk is called the Pasturisation.
(11) Medicinal Use of Microorganisms
(a) Antibiotics
Antibiotics is a type of medicine produced with the help of microorganisms. Antibiotics destroy or stop the growth of infectious bacteria. Since these medicines act against bacteria, thus are called antibiotics (anti + bacteria). Antibiotics come in the form of tablets, syrup and injections, which are given according to need to the sick people. Steptomycin, tetracyclin, cloxacyclin, erythomycin, etc. are the name of some antibiotics available in the market.
Antibiotics are also mixed with the feed of livestock and poultry to prevent microbial infections in animals. Antibiotics are also used to control many plant diseases.
(b) Discovery of Antibiotics
Sir Alexander Fleming, who was a British Scientist, discovered Antibiotics in 1929. He prepared the penicillin, an antibiotic. Sir Alexander Fleming honoured with Noble Prize for the discovery of antibiotics.
(c) Vaccine
Whenever any harmful microorganism enter in our body, our body produce antibodies. These antibodies destroy and stop the growth of the foreign as well internal harmful microorganisms. Our body also remembers how to fight against the microbe if it enters again. Based on this theory of mechanism of body vaccines are prepared. If dead or weakened microbes are introduced in a healthy body, the body fights and kills them by producing suitable antibodies. The antibodies so produced remain in the body and protect us from disease causing microbes.
Particular type of dead or weakened microbes are introduced in our body as a vaccine, as type of medicine, to enable us to protect from that particular disease.
Several diseases, including cholera, tuberculosis, smallpox, and hepatitis B, etc. can be prevented by vaccination.
(d) Discovery of Vaccine for Small Pox
An English Scientist, Edward Jenner, discovered the vaccine for small pox in the year of 1798. Because of vaccine discovered by him, the life of millions of people was saved from small pox and small pox has been eradicated completely. Before the discovery of vaccine, small pox was an epidemic.
(12) Increasing the Soil Fertility
Microorganisms also help to increase the fertility of soil. Some bacteria and blue green algae are able to fix nitrogen from the atmosphere to enrich soil with nitrogen and increase its fertility.
These microorganisms absorb nitrogen from atmosphere and made available in the soil in soluble form. Plants absorb this soluble nitrogen from soil and sythesise nutrition.
The process of making available of nitrogen in soluble form in the soil is called Nitrogen Fixation and microorganisms who are responsible for this are called Biological Nitrogen Fixers.
(13) Cleaning the Environment
Microorganisms are natural decomposer. This is the cause that dead animals and plants are disappeared after sometimes due to decomposing by microorganisms. Environment becomes clean after vanishing out of dead animals and plant after decomposing by microorganisms. This process of decomposing of dead animals and plants eventually replenishes nutrients back to the ecosystem, thereby, allowing the plants to grow.
(14) Harmful Microorganisms - Pathogens
Many microorganisms are harmful for us. Such disease causing microorganisms are known as PATHOGENS.
Harmful microorganisms are caused for several diseases in animals as well as in plants. Some microorganism spoils even food, clothes, and articles made of leather.
(15) Disease causing Microorganisms in Humans
Pathogens make people diseased after entering in their bodies through air, drinking water and food they eat.
Diseases causing pathogens (microorganisms) are transmitted also through direct contact with an infected person or carried through animals.
Microbial diseases that can spread from an infected person to a healthy person through air, water, food or physical contact are called communicable diseases. Cholera, common cold, chicken pox and tuberclulosis, etc. are example of such communicable diseases.
(16) Pathogens carrying Insects and Animals
Housefly, rats, street dogs, cats, etc. are carriers of pathogens, i.e. disease causing microbes.
(a) Pathogens carrying flies
Flies sit on garbage and pathogens present in the garbage stick to their legs and bodies. And when these flies sit on food, they may transfer pathogens stick to their bodies to the food. By transferring of pathogens to the food, food gets contaminated. A person taking those contaminated food likely to get sick.
(b) Pathogens carrying mosquitoes
(i) Parasite of Malaria Carrying Mosquito – Female Anopheles
Female Anopheles mosquito carries the parasite of malaria. These female Anopheles mosquitoes transfer pathogens while biting a person and make him sick. Malaria is a deadly disease and seeks immediate medical treatment.
(ii) Dengue carrying Mosquito – Female Aedes
Female Aedes mosquitoes carry the virus of dengue. It transfer dengue virus while biting a person. Dengue is a deadly disease and require immediate medical attention.
(c) Prevention from Mosquitoes
Mosquitoes breed in stagnant water. Some of the preventive measures to stop the breeding of mosquitoes and to avoid get bitten by mosquitoes.
(a) Water should not be allowed to collect anywhere, in collers, tyres, flower pot, etc.
(b) By keeping surroundings dry the breeding of mosquitoes can be controlled.
(c) We should use of mosquitoes repellents to keep the mosquitoes out.
(d) Mosquito net should be used in night.
By taking above preventive measures we can prevent ourselves from getting sick.
(17) Disease causing Microorganisms in animals
Several microorganisms are responsible for disease in animals.
Example: Anthrax is a dangerous human and cattle disease. Certain type of bacterium called Bacillus antracis is responsible for Antrax.
Bacillus Antracis responsible for Antrax
Referece: Y tambe [CC BY-SA 3.0], via Wikimedia Commons
Bacillus anthracis was the first bacterium to be used to prove that bacteria caused diseases.
Foot and mouth disease of cattle is caused by a virus.
Rabies is a viral disease that affects animals like dogs, cats, and money, etc. It spread even in human through saliva of animals having rabies.
(18) Disease causing Microorganisms in Plants
There are many microorganisms which are cause of diseases in plants. Such diseases. The disease reduces the yield of crops and sometimes even destroys the crop completely.
Example :
(a) Citrus canker is a lemon plant disease caused by bacteria. Mode of transmission of Citrus canker is air.
(b) Rust of wheat is a wheat plant disease caused by microorganism called Fungi and it spread by air and infected seeds.
(c) Yellow vein mosaic is a disease of plant of lady finger (bhindi or okra) caused by the virus and spread by insect.
Plants diseases can be controlled by using certain chemicals which kill microbes.
(19) Food Poisoning
Microorganisms that grow on our food sometimes produce toxic substances which make the food contaminated and poisonous. Contaminated food may be a cause of serious illness and sometimes even death.
Illness caused because of taking of poisonous food is called Food Poisoning.
(20) Food Preservation
Foods are preserved for ancient times. Keeping of food for long time edible, is called Food Preservation. Some methods of preserving food.
(a) Chemical Methods to Preserve Food
Salt and edible oil are capable to stop the growth of microorganisms, thus salt and edible oils are called Preservatives. So, salt and edible oils are used to preserve foods.
In pickling salt, edible oils and edible acids are used. These preservatives stop the growth of microorganisms.
Sodium Benzoate and Sodium Metabisalphite are also used as preservatives. These chemicals are used in making of jam, jelly and squash. Using these chemicals jam, jelly and squash stop the growth of microbes and keep these food items usable for long time.
(i) Preservation of Food by Common Salt
Common salt is a natural preservative. Covering of foods, such as meat and fish by dry common salt stops the growth of microorganisms. Salt absorbs the moisture present in foods. Microorganisms do not grow in the absence of moisture as they require moisture to grow.
(ii) Preservation of food by Sugar
Sugar also absorbs the moisture and check the growth of microorganisms which spoil foods. Jams, jellies and squashes are preserved by using sugar.
(iii) Preservation of Food by Oil and Vinegar
Microorganisms like bacteria and fungi cannot live in oil and vinegar, and thus edible oil and vinegar are used to preserve foods. Vegetables, fruits, fish and meat are often preserved by using edible oil and vinegar.
(iii) Preservation of food by Heat and Cold Treatments
Heat kills many microorganisms and cold stops the growth of microorganisms. Thus, food items are preserved by heat and cold treatments.
Boiling of milk kill many microorganisms and is stored for some long times.
In similar way cold environment stops the growth of microbes. Thus milk and other food items are refrigerated to preserve them for long hours.
(21) Pasteurization
Pasteurization is a method to keep milk usable for long time. In the process of Pasteurization milk is heated to about 70o C for 15 to 30 second and suddenly chilled and stored. This process prevents the growth of microbes. Pasteurized milk can be consumed without boiling as it is free from harmful microbes.
Louis Pasteur, a French scientist, discovered the process of Pasteurization. This process got its name as Pasteurization in the honour of its discoverer.
(22) Storage and Packing
In the absence of air growth of microbes is checked. Thus, food items can be preserved for long time by keeping them in the absence of air.
Vegetables, fruits, dry fruits, potatoes chips, wafers, sweets, etc. are sold in sealed air tight packets and cans to prevent the attack of microbes. In the absence of oxygen in sealed packets microbes do not grow as they require oxygen for their survival. This keeps the food items long time usable.
(a) Nitrogen filled food packets
Sometimes nitrogen is filled in the sealed air tight packet. Nitrogen and absence of oxygen stop the growth of microbes which keep the food usable for long time.
(23) Nitrogen Fixation
Nitrogen is essential for all living organisms. Nitrogen is one of the most important constituents of proteins, chlorophyll, nucleic acid and vitamins which are essential for living organism. So, it becomes essential that our atmosphere should have adequate amount nitrogen.
Our atmosphere contains about 78% of nitrogen gas. And this percent of nitrogen gas is fixed in the atmosphere.
Some microorganisms keep the nitrogen fixed in the atmosphere. Such microorganisms may be called nitrogen fixers or nitrogen fixing microorganisms.
Inspite of presence of adequate amount of nitrogen in the atmosphere, plants and animals cannot take nitrogen directly in that form.
(24) Nitrogen Cycle
Plants take nitrogen from soil only. There are certain bacteria and blue green algae present in the soil fix nitrogen from the atmosphere and convert it into compound of nitrogen which is usable form for plants.
A bacterium called Rhizobium lives in the root nodules of leguminous plants, such as beans and peas, which it has a symbiotic relationship. The Rhizobium takes nitrogen from atmosphere and convert it into usable form and makes available in the soil. Plants absorb the usable form of nitrogen from 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 animal die, bacteria and fungi present in the soil covert the nitrogenous wastes into nitrogen compounds to be used by plants again.
Certain bacteria convert some part of nitrogenous compounds present in dead animals and plants into nitrogen gas, which goes back into the atmosphere.
Sometimes action of lightning also fixes nitrogen in the atmosphere.
As a result the percentage of nitrogen in the atmosphere remains contestant.
Ref: Image is taken from NCERT Science Book, class 8, page number: 27
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