Fish Viruses Microbiology

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    VIRUSES

    UY - 2011

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    Are Viruses Living orAre Viruses Living or

    NonNon--living?living? Viruses are both and neither

    They have some properties of lifebut not others For example, viruses can be killed,

    even crystallized like table salt

    However, they cant maintain aconstant internal state(homeostasis).

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    What a Virus Isnt

    Not a bacterium...

    Not independent... Cannot survive in absence of a living cell

    within which to replicate...

    Antibiotics generally dont work on them...

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    Whatare Viruses?Whatare Viruses?

    A virus is a non-

    cellular particle madeup of genetic materialand protein that can

    invade living cells.

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    What Viruses Are...

    Infectious agents composed mainly of nucleic acid

    with a protein coat (capsid)

    Visible with electron microscope (10-200 nM)

    Carry on normal cell-like function (unless free, then

    infectious)

    In infectious form: no growth; no respiration??? Can enter living plant, animal or bacterial cell

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    Discovery of VirusesDiscovery of VirusesBeijerinck (1897)coined the Latin namevirus meaning poison

    He studied filteredplant juices & foundthey caused healthyplants to become sick

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    Tobacco Mosaic VirusTobacco Mosaic Virus

    Wendell Stanley(1935) crystallized

    sap from sicktobacco plants

    He discovered

    viruses were made ofnucleic acid andprotein

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    SmallpoxSmallpox

    Edward Jenner (1796)developed a smallpoxvaccine using milder

    cowpox virusesDeadly viruses aresaid to be virulent

    Smallpox has beeneradicated in theworld today

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    Viewing VirusesViewing Viruses

    Viruses areViruses are smallersmallerthan the smallest cellthan the smallest cell

    Measured inMeasured in

    nanometersnanometersViruses couldnt beViruses couldnt beseen until theseen until the electronelectronmicroscopemicroscope waswasinvented in theinvented in the 2020thth

    centurycentury

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    Electron Microscopy

    Mitra, K. & Frank, J., 2006. Ribosome dynamics: insights from atomic structure modeling into cryo-electron

    microscopy maps.Annual review of biophysics and biomolecular structure, 35, 299-317.

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    X-ray Crysta

    llography of Viruses

    Symmetry of protein shells makes them uniquely

    well-suited to crystallographic methods

    Viruses are the largest assemblies of biological

    macromolecules whose structures have been

    determined at high resolution

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    ViralViralStructureStructure

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    Virus Appearence? 1. Capsid

    2. Core and genetic material (DNA/RNA)

    Capsid: outer shell of the virus which encloses genetic material

    (link: chemical structure of capsid helps determine immune

    response to virus)

    capsid is made of many identical individual proteins

    protein core under capsid protecting genetic material

    sometimes an additional covering (lipid bilayer w/embedded

    proteins) on outside known as an envelope ( like a baseball)

    various forms: rods, filaments, spheres, cubes, crystals

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    CharacteristicsCharacteristics

    Non living structures

    Noncellular

    Contain a protein coat called thecapsid

    Have a nucleic acid core containing

    DNA or RNA Capable of reproducing only when

    inside a HOST cell

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    CharacteristicsCharacteristics

    Some viruses areenclosed in anprotective envelope

    Some viruses may havespikes to help attach tothe host cell

    Most viruses infectonly SPECIFIC hostcells

    CAPSID

    ENVELOPE

    DNA

    SPIKES

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    CharacteristicsCharacteristics

    Viral capsids(coats) are madeof individualprotein subunits

    Individual

    subunits arecalled capsomeres CAPSOMERES

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    Capsid

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    capsomere: unit/molecule associated with capsid structure

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    CharacteristicsCharacteristics

    Outside of host cells,viruses are inactive

    Lack ribosomes and

    enzymes needed formetabolism

    Use the raw materials

    and enzymes of the hostcell to be able toreproduce

    EBOLAVIRUS

    HIVVIRUS

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    Size of VirusesSize of Viruses

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    Viral ShapesViral Shapes

    Viruses come in a variety ofshapes

    Some may be helical shape likethe Ebola virus

    Some may be polyhedral

    shapes like the influenza virusOthers have more complex

    shapes like bacteriophages

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    T

    ypical

    Virus Shapes

    RODS SPHERES

    CUBES

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    The Structure of Viruses

    Tobacco

    Mosaic

    Virus

    HIV

    Bacteriophage

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    Helical VirusesHelical Viruses

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    Polyhedral VirusesPolyhedral Viruses

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    More Virus Shapes

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    Complex VirusesComplex Viruses

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    Taxonomy ofTaxonomy of

    VirusesViruses

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    ira Taxonomyira TaxonomyExamplesExamples

    Herpesviridae

    Herpesvirus

    Human herpes virus 1, HHV 2, HHV 3

    Retroviridae

    Lentivirus Human Immunodeficiency Virus 1, HIV 2

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    Herpes VirusHerpes Virus

    SIMPLEXI and II

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    AdenovirusAdenovirus

    COMMONCOLD

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    Influenza VirusInfluenza Virus

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    PapillomavirusPapillomavirus Warts!Warts!

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    RNA or DNA Virus

    Do or do NOT have an envelope

    Capsid shape

    HOST they infect

    Used for VirusUsed for Virus

    IdentificationIdentification

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    Bacteriophages

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    UY - 201137

    PhagesPhages

    Viruses that attackbacteria are calledbacteriophage or just

    phageT-phages are aspecific class of

    bacteriophages withicosahedral heads,double-stranded DNA,and tails

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    TT--phagesphages

    The most commonly studiedT-phages are T4 and T7They infect E. coli , an

    intestinal bacteriaSix small spikes at the baseof a contractile tail are usedto attach to the host cellInject viral DNA into cell

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    EscherichiaColi

    Bacterium

    T - EVENPHAGESATTACKTHISBACTERIUM

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    E. Coli and the

    Bacteriophage

    What it looks like in real

    life

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    T-Even Bacteriophages

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    Diagram of TDiagram of T--44BacteriophageBacteriophage

    Head with 20triangular

    surfacesCapsidcontains DNA

    Head & tailfibers madeof protein

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    Composition ofT-Even

    Bacteriophage

    Capsid: brains of virus,

    tightly-wound protein

    protecting nucleic acids Body: attached to

    capsid head, rod-like

    structure w/retractible

    sheath, hollow core

    Tail: at end of core is a

    spiked plate carrying 6

    slender tail fibers,

    anchor virus to its host

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    R

    et

    rovirusesR

    et

    roviruses

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