PG AND RESEARCH DEPARTMENT OF MICROBIOLOGY - SRI PARAMAKALYANI COLLEGE - ALWARKURICHI

1. SRI PARAMAKALYANI COLLEGE
( Reaccredited with B Grade with a CGPA of 2.71 in the II Cycle by NAAC
Affiliated to Manonmaniam Sundaranar University, Tirunelveli)
ALWARKURICHI 627 412 TAMIL NADU, INDIA
POST GRADUATE & RESEARCH CENTRE - DEPARTMENT OF MICROBIOLOGY
(Government Aided)
II SEM - CORE –VIROLOGY
UNIT – 1
DISCOVERY OF VIRUSES
A.ARUL SELVAM
REG NO: 20211232516105
I M.SC.MICROBIOLOGY
ASSIGNED ON:
TAKE ON :
Submitted to,
GUIDE: Dr.C.MARIAPPAN, Ph.D,
ASSISTANT PROFESSOR,
SRI PARAMAKALYANI COLLEGE,
ALWARKURICHI.

2. DISCOVERY OF VIUS AND EARLY
DEVELOPMENT
WHAT IS VIRUS ?
• virus, infectious agent of small size and
simple composition that can multiply only in living cells
of animals, plants, or bacteria. The name is from a Latin
word meaning “slimy liquid” or “poison.”
STUDY OF VIRUS ?
• the branch of science that deals with the study of
viruses.

3. FIRST DISCOVER :
Although Louis Pasteur and Edward Jenner developed the
first vaccines to protect against viral infections, they did not
know that viruses existed.
The first evidence of the existence of viruses came from
experiments with filters that had pores small enough to
retain bacteria
Louis Pasteur (1822–1895) was unable to find a causative
agent for rabies and speculated about a pathogen too small
to be detected using a microscope.

4. Charles Chamberland :
In 1884 ,the French microbiologist Charles
Chamberland (1851–1931) invented a filter – known today as
the Chamberland filter – that had pores smaller than
bacteria. Thus, he could pass a solution containing bacteria
through the filter and completely remove them from the
solution.
Adolf mayer :
In 1876, Adolf Mayer, who directed the Agricultural
Experimental Station in Wageningen, was the first to show
that what he called "Tobacco Mosaic Disease" was infectious.
He thought that it was caused by either a toxin or a very
small bacterium.

5. Dmitry Ivanovsky :
In 1892, the Russian biologist Dmitry
Ivanovsky (1864–1920) used a Chamberland filter to study
what is now known as the tobacco mosaic virus. His
experiments showed that crushed leaf extracts from infected
tobacco plants remain infectious after filtration. Ivanovsky
suggested the infection might be caused by a toxin produced
by bacteria, but did not pursue the idea.
Martinus Beijerinck :
In 1898, the Dutch microbiologist Martinus
Beijerinck (1851–1931), a microbiology teacher at the
Agricultural School in Wageningen repeated experiments
by Adolf Mayer and became convinced that filtrate contained
a new form of infectious agent.

6. He observed that the agent multiplied only in cells that were
dividing and he called it a contagium vivum fluidum (soluble
living germ) and re-introduced the word virus.
THE FIRST HUMAN VIRUS :
The first human virus to be identified was the yellow fever
virus. In 1881, Carlos Finlay (1833–1915), a Cuban physician,
first conducted and published research that indicated that
mosquitoes were carrying the cause of yellow fever .
A theory proved in 1900 by commission headed by Walter
Reed (1851–1902)
During 1901 and 1902, William Crawford Gorgas (1854–1920)
organised the destruction of the mosquitoes' breeding
habitats in Cuba, which dramatically reduced the prevalence
of the disease

7. THOMAS MILTON RIVERS (1888–1962) :
Rivers, a survivor of typhoid fever contracted at the age of
twelve, went on to have a distinguished career in virology.
In 1926, he was invited to speak at a meeting organised by
the Society of American Bacteriology where he said for the
first time, "Viruses appear to be obligate parasites in the
sense that their reproduction is dependent on living cells.
PROTEIN OR NUCLEIC ACID :
In 1935, Wendell Stanley examined the tobacco mosaic
virus and found it was mostly made of protein
In 1939, Stanley and Max Lauffer (1914) separated the
virus into protein and nucleic acid which was shown by
Stanley's postdoctoral fellow Hubert S. Loring to be
specifically RNA.

8. The discovery of RNA in the particles was important
because in 1928, Fred Griffith (1879–1941) provided the first
evidence that its "cousin", DNA, formed genes.
BACTERIOPHAGES :
Bacteriophages are the viruses that infect and replicate in
bacteria.
They were discovered in the early 20th century, by the
English bacteriologist Frederick Twort (1877–1950).
But before this time, in 1896, the bacteriologist Ernest
Hanbury Hankin (1865–1939) reported that something in
the waters of the River Ganges could kill Vibrio cholerae –
the cause of cholera.

10. The agent in the water could be passed through filters that
remove bacteria but was destroyed by boiling.
Twort discovered the action of bacteriophages
on staphylococci bacteria. He noticed that when grown on
nutrient agar some colonies of the bacteria became watery
or "glassy.
He collected some of these watery colonies and passed
them through a Chamberland filter to remove the bacteria
and discovered that when the filtrate was added to fresh
cultures of bacteria, they in turn became watery.[
He proposed that the agent might be "an amoeba, an
ultramicroscopic virus, a living protoplasm, or an enzyme
with the power of growth".

11. Félix d'Herelle (1873–1949) was a mainly self-taught French-
Canadian microbiologist. In 1917 he discovered that "an
invisible antagonist", when added to bacteria on agar,
would produce areas of dead bacteria.
The antagonist, now known to be a bacteriophage, could
pass through a Chamberland filter. He accurately diluted a
suspension of these viruses and discovered that the highest
dilutions (lowest virus concentrations), rather than killing
all the bacteria, formed discrete areas of dead organisms.
He realised that he had discovered a new form of virus and
later coined the term "bacteriophage"

13. THANKS TO