Microrganisms :Friend And Foe
The living organisms around us which we normally cannot see.These are called microorganisms or microbes.For example,during rainy season moist bread get spoil and its surface gets covered with grayish white patches.These microorganisms or microbes are so small in size that they cannot be seen with the unaided eye.Fungus can be seen with magnifying glass while others cannot be seen without the help of microscope.
Microorganisms are classified into four major groups.These groups are
- Bacteria
- Fungi
- Protozoa
- Algae
Viruses are also microscopic which reproduce only inside the cells of the host organism which may be a bacterium,plant, animal. Commom ailments like cold ,flu and diseases like polio chickengunia are caused by viruses.
Where do Microorganisms live?
Microorganisms can be single celled like bacteria and multicellular like algae,fungi.They can survive under all types of environmemt, ranging from ice cold climate to hot springs and deserts to marshy lands.They are also found in animal and human bodies.
Microorganisms and Us
Friendly Microorganisms
Microbes help to keep our environment clean by decomposing dead matter. They decomposed substances are recycled as these get reused from the soil by plants.
Some bacteria decompose sewage and other waste in water. This is nature’s method of keeping the environment free from pollution.
Making of curd and bread
Bacteria help us in making certain foods. Lactobacillus is a bacterium that sours milk and is used to makes curd from milk.
Many fungi like Mushrooms and morels are edible which are rich
Yeast is commonly employed in preparing food items like bread, cakes, idli, dosa, dhokla etc.
Yeast is also used in breweries for making wines by the process of fermentation.
Making medicines and vaccines:
Bacteria and fungi are used to make medicines called antibiotics.
The first antibiotic, penicillin was discovered by Alexander Flemming using the fungus penicillium.
Some common antibiotics are streptomycin and terramycin.
Microbes are used to make vaccines. Vaccines are weakened or dead germs introduced into the body. They offer protection against diseases like tuberculosis, polio etc. by producing anti- bodies.
Bacteria and Yeast are used in making vitamin B complex tablets.
The human hormonal called insulin can also be obtained from bacteria.
In Agriculture:
Some bacteria like Rhizobium, blue green algae like Nostoc, live in the root nodules of plants such as gram, pea etc. These bacteria absorb the nitrogen of the atmosphere and convert it into nitrate which serves as natural fertilizers for plants, hence, enhancing soil fertility.
Harmful Microorganisms
Microorganisms that cause diseases in human, animals and plants are called pathogens or germs.
Germs may enter the body of living organisms through air, contaminated food and water, from an infected person by direct or indirect contact or by a carrier.
Diseases that can spread from an infected person to a healthy individual through air, water or directcontact are called communicable diseases. Examples: Common cold, chicken pox, AIDS etc.
Micro organisms also cause diseases in animals and plants. For examples-
Anthrax is a disease caused by bacterium and affects human and cattle.
A virus causes the dangerous foot and mouth disease in cattle.
Citrus canker is a bacterial disease that affects trees of citrus fruits and is spread by air.
Rust of wheat is a viral disease that affects vegetable like bhindi & spread by insects.
Malaria is actually caused by pathogen called plasmodium (protozoa) which is transmitted by female Anopheles mosquito.
Dengue is caused by dengue virus and spread by Female Anopheles mosquito.
Preventing the spread of Communicable diseases:
Some simple methods of limiting the spread of communicable diseases are:
To keep the infected person separated from others & to advice his/ her to keep a handkerchief on the nose and mouth while sneezing.To keep our environment or surrounding clean.Never let garbage collect in the neighborhood.Timely vaccination against diseases should also be taken. To prevent mosquitoes from breeding we should not allow water to collect anywhere in our neighborhoods.
Many bacteria and fungi grow on food items and produce certain toxic substances. This makes the food unfit for consumption. Consuming such food can cause a serious illness called food poisoning.
Food preservation:
- Processing of food to prevent their spoilage and to retain their nutritive value for period is called food preservation.
- Food can be preserved using many methods:-
- Heating:heating food to a high temperature kills microbes. For example: Milk and water are boiled to kill microbes.
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- Cooling: food can be kept in refrigerator at about 5˚C which delays its spoilage.
- Canning: canning is done to package or preserve food or drink by putting it in sealed, airtight containers.
- Salting: Fruit and vegetables can be preserved by using salt and then drying. Salts prevent the growth of microbes.
- Sweetening: Excess sugar can also works on the same principle as salting. Jams, jellies & squashes are preserved by this method.
- Dry or dehydration: Dehydration of food remaining water from it. This stops microorganisms from growing as they cannot grow without water.
Chemical preservatives: Chemicals like sodium benzoate and sodium metabisulphite prevent microbial attack and are often use to preserve jams, sauces & ketchup
EXERCISES
1) a)microscope
b)nitrogen
c)yeast
d)bacteria
2) a)ii)alchohol
b)ii)streptomycin
c)i)female anopheles mosquito
d)ii)housefly
e)iii)growth of yeast cells
f)iii)fermentation
3)i)-e
- ii) -a
iii)-b
iv)-c
v)-d
vi)-f
4)Microorganisms cannot be seen through our naked eyes. Because they are very small in size Microorganism like fungus growing on bread can be seen with a magnifying glass while others can be seen with the help of microscope
5) Microorganisms are classified into four major groups.These groups are
- Bacteria
- Fungi
- Protozoa
- Algae
6)Rhizobium,Clostridium,Azotobacter
7)M icro-organisms are too small to be seen through naked eyes. However, they are vital to plants and the environment.
Importance of micro-organisms:
- They are used in winemaking, baking, pickling, and other food making processes.
ii. Alcoholic fermentation by yeast is widely used in the preparation of wine and bread. A bacterium Lactobacillus, promotes the formation of curd.
iii. Yeast reproduces rapidly and produces carbon dioxide during respiration. Bubbles of the gas fill the doughand increases its volume.
iv. Microbes are used to reduce pollution. For example, decomposers such as bacteria and fungi break down dead bodies and excreta to form inorganic compounds, which can be absorbed by plants.
v. They are used to increase the soil fertility by fixing the atmospheric nitrogen with the help of bacterium Rhizobium and some other blue-green algae.
vi. Microbes also play an important role in the preparation of medicines.
vii. Antibiotics are chemicals produced by micro-organisms to kill bacteria. Streptomycin, for example, is an antibiotic.
viii. Certain microbes are also used in the biological treatment of sewage and industrial effluents.
ix. Antibiotics are used to control many plant diseases.
x. Antibiotics are mixed with the feed of livestock and poultry to check microbial infection in animals.
8) Microorganisms are also very harmful to us. They cause a number of diseases inhuman as well as in other animals. Common cold, Tuberculosis, Measles, Chicken Pox, Polio, Cholera, Typhoid, Hepatitis B, Malaria, are some common human diseases caused by microorganisms. Anthrax is a serious disease in animals caused by microbes. They also make food items unfit for use by food poisoning. They also spoil clothes and leather products. They also cause diseases in plants like blights in potatoes, sugarcanes, oranges etc. They also reduce the crop production.
9)The medicines which kill or stop the growth of microorganisms in our body are called antibiotics. These are very useful to us as they prevent us from the effects of microorganisms. Antibiotics are made from bacteria and fungi. The penicillin is the first antibiotics which is discovered by Alexander Fleming in 1929. These days a number of antibiotics are used to cure various human and animal diseases. Streptomycin, Tetracycline, Erythromycin etc. are some common antibiotics. Precautions: We should take antibiotics only by the advice of a qualified doctor. Antibiotics should only be taken when needed. Otherwise, they may be harmful and become less effective in future.
