Microorganisms: Friend And Foe

(a) Microscope

Microorganisms are single celled organisms and cannot be seen by the naked eyes. A Microscope helps us see these microorganisms.

(b) Nitrogen

The blue green algae help fix 90% of the atmospheric nitrogen and play an important role in the nitrogenycle.

(c) Yeast

(d) Bacteria

(a) Yeast is used in the production of

(ii) alcohol

(b) The following is an antibiotic

(ii) Streptomycin

(c) Carrier of malaria-causing protozoan is

(i) female Anopheles mosquito

(d) The most common carrier of communicable diseases is

(ii) housefly

(e) The bread or idli dough rises because of

(iii) growth of yeast cells

(f) The process of conversion of sugar into alcohol is called

(iii) fermentation

(i) (e); (ii) (a); (iii) (b); (iv) (c); (v) (d); (vi) (f)

Micro-organisms are too much smaller that they cannot be seen with naked eye. They can be seen with a magnifying glass called microscope. For example, fungus that grows on bread is so small that it can be seen only with the help of a magnifying glass or microscope.

There are five major groups of micro-organisms. These are bacteria, viruses, protozoa, some fungi and Algae.

(a) Bacteria − They are single-celled disease-causing micro-organisms. They can be spiral or rod-shaped. Examples- Lactobacillus bacteria.

(b) Virus −These are disease-causing microbes that reproduce only inside the host organism. Example- HIV.

(c) Protozoa − They can be unicellular or multicellular. Example- Plasmodium.

(d) Fungi − They are mostly multicellular. Bread moulds are common examples of fungi.

(e) Algae − They include multicellular, photosynthetic organisms such as Spirogyra, Chlamydomonas, etc.

Certain bacteria such as Rhizobium and blue green algae present in the soil fix atmospheric nitrogen and convert it into compounds of nitrogen.

Microorganisms are used for various purposes such as:

1. They are used in the preparation of curd, bread and cake.

2. They are used in the preparation of alcohol, wine and acetic acid (vinegar).

3. They are also used in cleaning up of the environment.

4. In agriculture, they are used to increase soil fertility by fixing nitrogen.

5. The antibiotics are manufactured by growing specific microorganisms and are used to cure a variety of diseases. Penicillin is an antibiotic made from Penicillium.

6. Certain microbes are also used in the biological treatment of sewage and industrial effluents.

7. Bacteria present in our gut helps in proper digestion of food

8. Microorganisms are also used for preservation of food items

9. Yeast is used in making idlis, bhaturas, bread, pastries and cakes.

10. Microorganisms are also used in processing and aging of cheese

Microorganisms are harmful in many ways. Some microorganisms cause disease in human beings, animals and plants. For example, in humans, bacteria cause diseases such as tuberculosis, cholera, typhoid, etc. Similarly, in plants, bacteria cause a disease called citrus canker. Such disease-causing microorganisms are called pathogens. .During our lifetime we come in contact with many microorganisms . Some of these leave undesirable characteristics on our body .They release some harmful materials called toxins . These make the food poisonous causing serious illness and even death. For example, bread when left unused under moist conditions gets spoil by fungus, producing a white cotton-like growth on the bread.

Medicines which kill or stop the growth of the disease-causing micro-organisms are called antibiotics.
Streptomycin, tetracycline and erythromycin are some of the commonly known antibiotics which are made from fungi and bacteria.

Some of the precautions should be taken while taking antibiotics which are as follows:

1. Antibiotics should be taken only on the advice of a qualified doctor.

2. A person must finish the full course of antibiotics prescribed by the doctor.

3. Antibiotics should be taken in the right amount and at the right time.

4. Antibiotics should not be taken unnecessarily.