Micro-organism: Virus, Bacteria, Algae, Fungi, Protozoa

Micro-organism: Virus, Bacteria, Algae, Fungi, Protozoa

Posted by Sarkari-Form.com

Sunday, December 08, 2019

Science and Fiction

What are micro-organisms?

(Micro-organisms)

Among all forms of living organisms existing on the earth, there are few that you can see with your naked eyes whereas there are many others that you fail to see with your naked eyes. These living organisms that you fail to see with your naked eyes are called 'micro-organisms'.

(Antonie van Leeuwenhoek)

The knowledge of their existence came after the discovery of cell by Robert Hooke in 1665 when Antonie van Leeuwenhoek observed the first living cell in a drop of pond water. The organism observed by him were bacteria. Later in 1857, Louis Pasteur with the germ theory and concept of vaccination proposed and laid the foundation of 'microbiology'.

Microbiology is the branch of science that deals with the study of micro-organisms. Louis Pasteur is known as the father of microbiology for his discovery of vaccines for rabies, anthrax and for the simple but well-known technique of 'pasteurization'.

Activity
Take a drop of pond water on a slide. Place the coverslip on the drop of pond water. Using the higher magnification of the microscope, observe the water drop. Record your observations.

Where do micro-organisms live? 

(Amoeba)

They can survive under all types of environments, 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 micro-organisms grow on other organisms while others exist freely. Micro-organisms like amoeba can live alone, while fungi and bacteria may live in colonies.

Types of micro-organisms 

The micro-organisms, found on the earth, differ from each other like the rest of the organisms that you see in your surroundings. All these micro-organisms have been classified into five different categories. These are viruses, bacteria, algae, fungi, and protozoa.

Viruses: These cannot be seen through a simple microscope. To see viruses we need a very powerful electron microscope. These are the smallest of all micro-organisms. These consist of nucleic acid covered with the protein shell. Viruses exhibit a variety of shapes, having a simple structure. Viruses are living only inside living organisms and remained non-living outside living organisms. They can cause many diseases.



Bacteria: Bacteria are responsible for the largest number of diseases as compared to any other micro-organisms. They vary in their shapes, sizes, and habitats (dwelling places). In size they have range from 0.2 to 100 microns, with the smallest bacteria known is 0.15 micron and, the largest is 1.5 micron in diameter and 15 micron in length (1 micron = 1/1000 mm or 1ｘ10^-6 metre).



Bacteria are unicellular micro-organisms. They do not have a define cellular nucleus. These are divided into four groups based on their shape: Cocci, Bacillus, Spirillum and Vibrio. Some bacteria live on their own whereas others are dependent and form colonies. These further can be classified into three groups depending on their response to gaseous oxygen: aerobic - that needs oxygen to survive, anaerobic - that can live without oxygen and anaerobes - this can live in both environments.

Algae: Algae are a group of eucaryotic oxygenic photosynthetic micro-organisms that contain chlorophyll (as seen in plants). Algae range from single-celled organisms to complex multicellular organisms like seaweeds. Algae inhabit a wide range of habitats from aquatic environments (freshwater, marine, and brackish) to soils and rocks; only inadequate light or water seems to limit the presence of algae. Algae are most commonly found in saturated environments either suspended (planktonic), attached to surfaces, or at the air-water interface (neustonic).



Fungi: The fungi may appear to be plants, but they do not have leaves, roots, and chlorophyll. These are simple non-green plants that are not photosynthetic, they are heterotrophic. Some fungi such as Puccinia, Albugo, Ustilago, etc. are parasites, drawing their nutrients from living cells of the host plants. They may be unicellular.

Activity
Visit a pond and collect some green scum floating on its surface. Wash the collected scum, and place a little of it on a glass slide. Properly spread the mesh of the scum, and observe it using a microscope. Record your observations in the form of a labeled diagram.

Protozoa: Protozoa are unicellular (one-celled or single-celled) mostly aquatic. They are solitary or colonial, free-living for parasitic or symbiotic. Their body shape may be irregular, spherical, oval, elongated and flattened.

Useful micro-organisms 

Micro-organisms are used for various purposes. All viruses, some bacteria, and some fungi are harmful but most micro-organisms are beneficial. Let us discuss some useful micro-organisms.

Useful Bacteria

1. Most bacteria are decomposers. Some decompose plant and animals remains, and release minerals into the soil and carbon dioxide into the air. Some act on nitrates in the soil and release nitrogen into the air. We use bacteria to treat sewage and to produce biogas from waste. We have also started using them as clean up oil spills.

2. Nitrogen-fixing bacteria draw nitrogen from the air and convert it into ammonia, nitrites, and       

(Nitrogen-fixing bacteria
in the root of the plant)

nitrates, which enrich the soil. Some bacteria help to dissolve minerals present in the soil. Plants cannot absorb these minerals unless they are redissolved.

3. Herbivorous, like cows and goats, can digest grass because of the presence of cellulose-digesting bacteria and their stomach. Human beings also benefit from the presence of some beneficial bacteria in their intestine.

4. Certain bacteria are used to make antibiotics. Some others are used for industrial production of vinegar, ethyl alcohol, butanol, and organic acids. Bacteria are also used to make enzymes, vitamins hormone, proteins, and other useful biochemicals.

5. Certain types of bacteria are used for the tanning of leather, and the curing of tea and coffee.

6. Some bacteria are very useful to use research tools in molecular biology, biochemistry, and biotechnology. Major discoveries related to the structure and function of genes protein synthesis and immunology has been made as a result of studies on bacteria.

Useful Fungi

1. Most fungi are decomposers. They add nutrients to the soil by decomposing organic matter.

2. Penicillium, a soil fungus, is used to originally produce in 1940; penicillin was the first antibiotic to be made.

3. Yeast used for the production of wine and other alcoholic beverages, bread, idli, dosa, and many other fermentative products, is a fungus. It is also used to produce proteins and vitamins.

(Mushroom)

4. Mushroom and morels are also fungi. These are widely cultivated and eaten for their taste and nutritive value.

5. Some fungi are also used as tools of research in Genetics and Biotechnology.

Useful Algae

1. Algae not only supply food to aquatic animals but also release oxygen into the air through photosynthesis.

2. Some red algae are eaten in certain countries. Some are used as animal feeds, while others are used for making toothpaste, glue, jelly, and so on. Agar, used for chicken jelly and puddings, and in biological research is obtained from two types of red algae.

(Blue-green algae in the lake)

3. A few blue-green algae, like Nostoc and Anabaena, are very useful for agricultural as they enrich the soil with nitrogen. They are used mostly in rice fields.

4. Some brown algae are important sources of iodine and potash, while some are used to produce confections (sweets).

Note: All the viruses are not useful. They are all harmful.

Harmful micro-organisms 

Micro-organisms are harmful in many ways. Some of the micro-organisms cause diseases in human beings, plants, and animals. Some spoil food, clothing, and leather.

We can classify various diseases according to the type of causative organism or pathogen.

Disease	Mode of Transmission	Causative Pathogen	Preventive Measures
Malaria	Bite of the female Anopheles Mosquito	Protozoa	Not allowing mosquitoes to thrive in the locality
Cholera	Contaminated food and water	Bacterium (singular form of Bacteria)	Maintain proper sanitation practices, Boiling water before drinking
Typhoid	Contaminated food	Bacterium	Maintain proper sanitation practices
Tuberculosis	Air	Bacterium	Vaccination
Ringworm	Direct contact with the infected person	Fungus (singular form of Fungi)	Good hygiene, Not sharing personal items
Common Cold	Air	Virus	Washing hands regularly, Avoiding close contact with people having the common cold
Poliomyelitis	Air and water	Virus	Vaccination
Chicken Pox	Air, physical contact with the infected person	Virus	Vaccination

How to avoid spreading harmful micro-organisms 

You can avoid spreading harmful micro-organisms by:

1. Washing your hands before eating, after preparing food, and after using the toilet.

2. Covering your mouth when you cough or sneeze.

3. Keeping away from other people if you have a disease that is easily spread.

4. Not eating food which is not fresh or has not been cooked properly.

5. Keeping uncooked meat separate from other foods in the fridge.

Food spoilage 

(Food spoilage)

When you keep bread outside the refrigerator for a few days, spongy growth is seen on it, which may be white, green and black in color. The bread thus gets spoilt due to the growth of mold and becomes unfit for consumption. Likewise, if cooked dal or vegetable is left outside for some time, it develops a bad smell and bubbles due to fermentation.

The dal and vegetables are spoilt and cannot be eaten. Can you now say when is a food spoilt?

Food is said to be spoilt if there is rotting i.e. bad smell, fermentation i.e. bubbles/gas in the food or mold i.e. spongy growth on the foodstuff. The formation of the soft spot on or soft brown spots on fruits and vegetables is also food spoilage.

(Stale food)

Micro-organisms spoil food items when the condition for their growth is appropriate. What are these appropriate conditions? Like all living beings micro-organisms require air, moisture, right temperature and food to grow and multiply. The situations which provide appropriate conditions for the growth of micro-organisms can be listed as:

1. Food having high moisture content.

2. Air around the food containing micro-organisms.

3. Food kept for a long time at room temperature.

4. Skin of fruits and vegetables getting damaged, thus exposing the food to micro-organisms.

5. Food with low salt, sugar or acid content.

Methods of preserving food at home 

Food can be preserved at home by the following methods:

1. Dehydration

2. Lowering temperature (freezing)

3. Increasing temperature

4. Using preservatives (canning)

Let's now discuss each method in detail.

Dehydration

Can you name some dried food items that are stored in your kitchen for a period of one year or more? Are these potato chips, sevia (vermicelli), methi, papad, ginger powder?

These are the foods that have been preserved by the dehydration method. The word dehydration means removing water or moisture from food. The home method of dehydration is sun drying. The most appropriate weather to dry food is when the air is dry and there is strong sunshine.

Lowering temperature

(Refrigerator)

Using low temperature to preserve food works on the principle that low temperature slows microbial and enzyme action. The food is thus prevented from spoilage. Are you using this method of preservation at home? Yes, if you have a refrigerator you can use it because a refrigerator work on this principle. Food can be preserved at low temperature by:

(a) Refrigeration -40⁰ C to -70⁰ C

(b) Cold storage -10⁰ C to -40⁰ C

(c) Freezing -180⁰ C or below

The duration for which the food can be preserved by using low temperature varies with the types of food and the temperatures. The lower the temperature, the longer is the duration for which food can be preserved. Of the three methods, freezing uses the lowest temperature.

Increasing temperature

By increasing the temperature, enzymes and micro-organisms are destroyed, leaving the food safe from spoilage. Do all organisms get killed by increasing temperature?

There are only two methods of preserving food by using high temperature:

(a) Pasteurization
(b) Sterilization

(a) Pasteurization: When you think of pasteurization, which food item comes to your mind? Yes, it's milk. We have often heard about pasteurized milk packets.



Note: The photo in the middle is of Louis Pasteur. He discovered the principle of Pasteurization.

In this method, food is heated to a high temperature and then quickly cooled. The micro-organisms are not able to withstand the sudden change in temperature and destroyed. However, some organisms still survive in this method.

(b) Sterilization: What does the word sterilization mean?

(Sterilization)

It means free from any living organism. The high temperature used in this method to destroy all the micro-organisms in the food. The foods are exposed to a high temperature for a long time and in some cases under pressure.

When a pressure cooker is used to cook, the food lasts longer because most micro-organisms get destroyed. You can also sterilize bottles and other pieces of equipment used in preservation.

Using preservatives

What are preservatives? Any substance that is added to food to keep it for a long time is called a preservative.

You have learned that increasing the concentration of salt, sugar or acid in food prevents its spoilage. Therefore salt, sugar or acid are the substances that act as preservatives.

There are two types of preservatives:

(Natural preservatives)

(a) Natural preservatives: Salt, sugar, lemon juice, vinegar, oil, and spices are natural preservatives.

(Chemical preservatives)

(b) Chemical preservatives: Potassium metabisulphate, citric acid, and sodium benzoate are chemical preservatives.

* Useful words 

Micro-organisms: The organisms that cannot be seen with naked eyes but can only be seen with the help of a microscope. 

Virus: The smallest of all micro-organisms, cause disease when in contact with living organisms.

Bacteria: Unicellular organism, not having a well defined cellular structure.

Algae: Photosynthetic micro-organisms, not differentiated into roots, stem or leaves.

Fungi: Heterotrophic in nature, maybe parasitic or saprophytic.

Protozoa: Unicellular, show animal-like characteristics cause diseases in man and animals.

Pathogens: Organisms that cause disease.


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Now, Answer time!

Answer the questions given below. Tell us your answers through the comment.
1. Name the different types of micro-organisms found in the atmosphere. 2. Name any two diseases caused by the virus. 3. Write any two uses of yeast. 4. Name any two edible fungi. 5. Name any two natural preservatives. 6. Name any two chemical preservatives. 7. Mention any two uses of algae.