The first
person to discover the existence of a viral disease in plants (TMV- Tobacco
Mosaic Virus) was a Russian, Dmitri
Iwanowski (1892). He demonstrated that TMV could be transmitted to healthy
plants through the sap from diseased plants even though the sap had been passed
through the filters fine enough to hold back bacteria.
In 1898, Beijerinick found that the filterable,
invisible and non cultivable infectious entity could diffuse through agar gel
like a fluid. He, therefore, called living infectious fluid as “contagium vivum fluidum”. In 1892 Louis Pasteur indicated that rabies is
caused by virus.
We know that
viruses reproduce and cause disease in animals plants and micro-organisms. They
are unable to propagate outside the cell. Thus they are obligate intracellular
parasite. The major breakthrough in virus history was made in 1930’s when
its physical and nature were known.
Viruses are
known as the connecting link between the living and non-living things.
FEATURES:
1. They are non cellular living
molecules
2. They are highly infectious
3. They have single nucleic acid.
4. They do not have the capacity to grow
and divide independently.
5. They reproduce from genetic material
only.
6. Absence of enzyme for energy
metabolism, i.e. they have no metabolic activity of their own.
7. Absence of ribosome.
8. Absence of the information for the
synthesis of ribosomal protein.
9. Absence of the information for the
synthesis of the ribosomal RNA and soluble transfer RNA.
Virus
consists of DNA or RNA but never both, surrounded by a protein sheath called
the capsid. DNA or RNA of a virus may
either be linear or circular and may be single stranded (ss) or double stranded
(ds).
Branch of
the science which deals with the study of the virus in detail is called VIROLOGY.
CONTRIBUTIONS OF THE DIFFERENT
SCIENTISTS TO THE FIELD OF VIROLOGY:
1. Viruses (from plants while studying
variation in tulip flowers) were first described by Carolus Clusius, in 1576.
2. Vaccination was introduced against
small pox by Edward Jenner, in 1796.
3. TMV was first reported first by Adolf
Mayer, in 1880.
4. The word virus (Latin-poison) was
coined by Louis Pasteur, in 1884.
5. The existence of virus was scientifically
proved by iwanowski, in 1892.
IWANOWSKI
6. Iwanowski’s observations were
confirmed after the discovery of the foot and mouth disease by Beijerinick,
Loefler and Frosch, in 1899.
7. Bacteriophages were discovered by
Twort de Herelle, in 1917.
8. The first to determine the chemical
composition of virus was Schelsinger, in 1933.
9. First to crystallize viruses and also
reported that crystals can cause disease was Stanley, in 1935.
10. Nucleoprotein nature of virus was
reported by Bawden and Pirie, in 1936.
11. Mutations in viruses were detected by
Delbruck, in 1938.
12. It was proved that DNA is the genetic material for
Bacteriophage by Hershey and Chase, in 1952.
13. Temperate viruses were discovered by
Lwoff, in 1953.
14. Cultivation of polio virus was done
by John F. Enders, in 1954.
15. Successive vaccination against polio
was given by John Salk and Albert Sabin, in 1957.
16. The viroid was discovered by
T.O.Diener, in 1971.
17. Retrovirus and the phenomenon, teminism was discovered by Temin and Baltimore, in 1972.
18. The first virusoid was discovered by
J.W.Randles, in 1981.
19. The presence of prion was first announced by
the University of California, in 1982.
20. AIDS virus was discovered by Lu
Montagnier et al and Robert Gallo, in 1983 and 1980 respectively.
21. Nobel Prize was given for the
description of CJD (Creutz feldt Jakob disease) and kuru to Stanley Prusiner,
in 1997.
COINAGE OF THE TERM 'VIRUS' IS DONE BY PASTEUR
STANLEY THE FATHER OF VIROLOGY
Still many
aspects of virology are left unknown. Many diseases caused by viruses have no
medicine. It’s one of the hot subjects in research field. By understanding and
giving interpretation about the activity of viruses, we can create wonders in
science……!!!
No comments:
Post a Comment