Virus 1
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Virus 1

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    Virus 1 Virus 1 Presentation Transcript

    • VIRUS
      • The development of virology
      • TMV virus
      • Lambda phage
      • HIV
    • The development of virology
      • Start of 20 th centaury
      • Infectious diseases attributed to parasitic fungi and bacteria
    • The development of virology
      • 1892
      • Tobacco mosaic disease induced in healthy plants by rubbing their leaves with juices from infected plants after filtering through bacterial filters
    • The development of virology
      • 1892
      • Foot and mouth disease shown to be passed on in bacterial filtered fluids from infected animals
    • The development of virology
      • 1898
      • Recognised that there must be a “new” type of infectious agent – the term “virus” introduced
    • The development of virology
      • Early 1900’s
      • Established that viruses propagate only in living cells, i.e. obligate intracellular parasites
      • Viruses capable of destroying Staphylococci identified
    • The development of virology
      • 1917
      • Viruses capable of destroying dysentery bacilli identified
      • Bacterial viruses now called bacteriophages .
    • The development of virology
      • 1930’s
      • Established that viruses are particulate, virus particles called virions .
    • The development of virology
      • 1935
      • Tobacco mosaic virus (TMV) purified
    • The development of virology
      • 1936
      • Established that TMV is a nucleo-protein capable of crystallization.
      • This suggests a simplicity and regularity to their structure
    • The development of virology
      • Subsequent studies
      • Possible to separate the protein and nucleic acid of viruses and demonstrate that the nucleic acid component alone is capable of initiating infection.
    • The development of virology
      • Structural and chemical composition of viruses
      • Understanding virus structure has been dependent upon the development of such methods as chromatography, electrophoresis, density gradient centrifugation, electron microscopy and X-ray diffraction
    • The development of virology
      • Structural and chemical composition of viruses
      • Simplest viruses, e.g. TMV, consist of only protein and nucleic acid
      • Viruses only ever have one type of nucleic acid
    • The development of virology
      • Three basic virus groups
      • RNA virus e.g. Tobacco mosaic virus, TMV
      • DNA virus e.g. bacteriophage
      • RNA retrovirus e.g. HIV
    • The development of virology
      • Most of the proteins in a virus occur as a coat, called a caspid, surrounding the nucleic acid
      • The protein protects the nucleic acid from hostile environmental conditions
      • The protein also aids the penetration of the host cell.
      • The outer coat (the caspid) is made out of sub-units called capsomeres, arranged in a helical pattern
    • Tobacco Mosaic Virus (TMV)
      • Rod shaped 300nm long, diameter 15nm
      • 94% protein,
      • 6% RNA
    • Tobacco Mosaic Virus (TMV)
      • Attacks tomato, blackcurrant, potato, orchid and tobacco.
      • Causes irregular mottled patches to appear on leaves of plants which indicate areas where cells and tissues have been killed by the virus
    • Tobacco Mosaic Virus (TMV)
      • Carried on seed coats, by grasshoppers and by other mechanical means
    • Tobacco Mosaic Virus (TMV)
      • Control measures include
      • Avoidance of growing susceptible crops in soil known to be contaminated
      • Sterilisation of soil used for seed beds
      • Hygienic handling of crops by workers
      • Use resistant varieties of crops
    • The lambda phage
      • Also known as:
      • T4-phage
    • The lambda phage
      • An example of a bacteriophage (A virus that uses bacterium as its host)
      • Invades the bacterium Escherichia coli
    • The lambda phage
      • Can destroy the host cell or insert its DNA into the bacterial chromosome and remain dormant for several generations
    • The lambda phage
      • Consists of a head, containing a double stranded DNA molecule wrapped around a core of protein surrounded by a polyhedral capsule and a helical tail.