DISCOVERY OF VIRUS.pptx

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) I I 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 . 

9. 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".

10. 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 "

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