Basic Information about viruses

We are in the middle of a pandemic which is caused by a virus. Viruses are ultramicroscopic, disease causing entity of organic matter, It can replicate or multiply only in the presence of a living host cell. They are called as entity because they exhibit both living and non living characters and it is difficult to conclude them as any one.


Russian botanist Dimitri Ivanovskii reported the virus for the first time in 1892. He explained tobacco mosaic virus. In 1898 M. W. Beijerinek recognized that viruses were smaller than bacteria, and they can easily pass through bacterial filters. In the same year, Friedrich Loeffler and P. Frosch, in Germany demonstrated the cause of Foot and mouth disease in cattles are due to viruses. In 1900 Walter Reed et al. explained yellow fever disease in humans was due to viruses. And in1915 F. W. Twort in England discovered bacteriophages.

In 1935 W. M. Stanley isolated Tobacco mosaic virus and crystalized. He explained that virus also contain proteins. In 1936 Bawden and Pirie demonstrated viruses to be nucleoproteins, they are made up of Nucleic acids and proteins. The major development was determining the ultrastructure of TMV by x-ray diffraction which was accomplished by R. Franklin and A. kling. Discovery of cyanophages was done in 1963.

What are the general characters of a virus
  • They are very small, so small that even they are not visible under compound microscope. Their size varies from 20nm to 400nm.
  • they are obligate parasites, They multiply only in the presence of a living host cell.
  • Viruses do not contain any type of cells.
  • Like Bacteria, viruses can not be cultured in labs on a synthetic media.
  • Viruses are highly specific. While infecting they just do not infect randomly any cell. They find specific cells for them which varies from virus to virus. They are also specific to tissues, organ, organism and species.
  • Viruses can be inactivated by heat or chemicals.
  • Viruses also lack metabolism. They are totally dependent on the host cell.
  • Viruses undergo mutation very often.

Living characters shown by viruses:

Are viruses living? we don’t know. But they contain nucleic acids which we consider the basis of life. As every other organism they have definite form and size. They grow and reproduce in the host cell. They can infect the host cells and cause diseases. They show mutation and inherit their characters to their reproduced offspring. These call characters are shown by living organisms.

non living properties of viruses:

Even though they exhibit some of the living characters as mentioned above they lack cellular organizations like other organisms. This arises the biggest confusion. They behave like non living outside the host cell. Some of the viruses can be crystalized and stored in bottles and jars. And they lack metabolism which is the basic characteristic of a living organism.

how viruses are classified?

The types of virus based on the hosts they infect includes, Bacteriophages- Which infect bacteria, Cyanophages- which infect blue green algae, phytophaginae-which infect plants and the Zoophages- which infect animals.

a bacteriophage

The viruses are considered to be DNA virus if the nucleic acid present in them is DNA and RNA virus if the nucleic acid present is RNA.

No matter how they are classified or what are their features, viruses are unique and mostly dangerous to animals. Even though vaccinations can help, Avoiding exposure to them will be the best way to keep oneself safe.

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