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Virus and Bacteria : Difference

Biology | 7-14 yrs | Reading Pod, Interactive

What is the difference between Virus and Bacteria?

We often hear the terms virus and bacteria in our daily lives, generally we hear these terms with reference to the diseases caused by them, but did you know that they have their advantages too. Let us understand what virus and bacteria really are.

What is Virus?

Viruses are extremely small substances made of nucleic acids (RNA – ribonucleic acid or DNA – deoxyribonucleic acid) and proteins, which can only be seen through an electron microscope. It is a small, infectious agent or parasite that cannot reproduce by itself, but it replicates inside the living cells of an organism. They do not live freely in nature, they live only inside other cells. They infect all organisms – from animals and plants to bacteria and archaea.

The word virus is derived from a Latin word which means‘ slimy liquid’ or ‘poison’. The plural of virus is referred to as viruses.

Viruses are found wherever there is the existence of life. They are believed to have existed since the evolution of living cells. Viruses spread in many ways, in plants they are often transmitted from one plant to another by insects. In animals they can be carried or transmitted by blood sucking insects.

Shapes of Viruses

Viruses are usually spiral shaped or shaped like soccer balls, some large viruses could be a combination of both shapes. Viruses take over the metabolism of their host cells. They usually kill the host cells after producing more virus. Viruses attack only one kind of host.

A virus is like a gene. It has no cell of its own, it depends on the host cell that it infects to reproduce. It produces more virus particles of its own kind through the host cell, eventually killing the host cell. The liberated virus particles then goes on to attack new host cells.

The virus inserts its genetic material into its host, taking over the host’s functions. The infected cells produce more viral protein. Some viruses may remain dormant inside their host cells for long periods causing no change in their host cells . Dormant viruses when stimulated, enter a phase called the‘ lytic’ phase, wherein the new viruses are formed and they burst out of the host cell killing it and move on to infect other cells.

When the virus is found outside the host cells , it exists as a protein coat which sometimes is enclosed in a membrane.

The damage done to the cell leads to the sickness or disease that we see. Different kinds of viruses cause different diseases. Certain common viral diseases are the common cold, influenza, small pox, rabies, HIV etc. There are no cures for viral diseases, though some of them can be prevented using vaccinations. Walter Reed discovered the first human virus, the yellow fever virus in the year 1901.

What is Bacteria?

Bacteria are the simplest form of living creatures . They are present almost every- where , even inside us. They are unicellular organisms ( organisms with a single cell – prokaryotes without a true nucleus).

We often hear or speak of bacteria in terms of the harm they cause, but it is important to note that they are also very helpful and can be tasty.

There are several species of bacteria found in the air, water, soil, food stuffs and even within living organisms.

They are the smallest living organisms on earth in fact they are very, very, very small in size.

4 Shapes of Bacteria –

  1. The spherical bacteria – Cocci
  2. Rod shaped bacteria – Bacilli
  3. The spiral shaped bacteria – Spirilla and
  4. The comma shaped bacteria called the Vibrio.

The word bacteria was derived from the word ‘bakterion’ meaning a small rod or staff, in the 19th century by Ferdinand Cohn.

The structure of each bacterium is very simple.

Bacteria consists of

  • A living substance called the protoplast.
  • The protoplast is surrounded by a cell wall which is non – living and stiff .
  • Beneath the cell wall, is a thin cell – membrane that surrounds the cytoplasm. The cytoplasm consists of the vacuoles, granules and in some rare cases it also contains some green pigment.
  • There is absence of a well defined nucleus, though the chromatin material called DNA is present in the central portion of the cell.

Most bacteria cannot move about on their own, they are transported by wind, water or through contact.
Since bacteria do not contain the green pigment found in plants, called chlorophyll, they are heterotrophic, that means they have to depend on ready – made food from various sources. They could be‘ saprotrophic’ or ‘ parasitic’ bacteria.
Saprotrophic bacteria are those bacteria that derive their nourishment from dead or decaying organisms.
Parasitic bacteria are those bacteria that draw their nourishment from the body of their living hosts.
Bacteria reproduce very fast through cell division.

Beneficial uses of Bacteria :-

  • The bacteria present in certain foods, like yogurt can actually prevent plaque from sticking to our teeth.
  • Bacteria is used in the fermentation of beans that go in to the making of chocolate.
  • Bacteria is used to preserve certain foods made from vegetables and are used to make some sauces used in cooking like the soya sauce.
  • They are used in the making of certain medicines like antibiotics, serums and vaccines.
  • They play an important role in agriculture. The bacteria present in the soil breaks down the soil nitrates thereby releasing nitrogen gas in to the air.

How do Bacteria cause disease?

  • Many bacteria tend to spoil cooked food especially during summer through fermentation thereby causing food poisoning.
  • In plants, bacteria causes two very common diseases, namely black rot of mustard and cauliflower and the bacterial blight of cowpea.
  • In animals, we commonly see the diseases like anthrax ( swelling on the body and reduction in the yield of milk ) and tuberculosis.
  • In humans, it causes diseases such as cholera, typhoid, tuberculosis, whooping cough, pneumonia etc.
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