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Blueboom/Atypical Virus like agents

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Atypical virus like agents

  • defective- complete virion but unable to replicate without helper virus
  • pseudovirons contain host DNA not viral, infectious but no replication

Prions

  • subviral particle , no nucleic acid
  • slow infection, long incubation period (months-years)
  • transmissible spongiform encephalopathies 1950's scrapie (hseep) kuru (and now BSE bovine spongiform encephalopathy

vproion sialoglycoprotein called PrP 27-30

  • Prp gene chromosome 20
  • Prp Protein (33-35) noninfectious -> Prp (27-30)
  • link to human disease
  • neurgenerative crytzfel-jacob disease transmissible spongiform encephalopahty progressive degeneration of the brain
  • nvCJD (new variant CJD)
  • suspect for alzheimers, multiple sclerosis
  • transmission horizontal (person to person, formites, eating contaminated meat)

Viroids

  • infectious agents/subviral particle
  • small circular ss RNA with/without capsid or envelope
  • mainly cause plant diseases recently identified hep D as a viroid
  • hep d is enclose in a hep b virus capsid
    • must be simulataneously infected with both hep b and hep D viroid

Bacterial viruses

  • bacteriophage/phage is a viral agent of bacteria

Structure

  • phage head : protein capsid (icosahedral symmetry) which surrounds nucleic acid (majority ds DNA)
  • tail: attached prtein (helical in structure which may have base end plate with spikes (pins and tail fibers which allows injection of nucleic acid in bacterial cell

Comparison

Character Bacteria Mycoplasma Chlamydiae Rickettsiae Fungi Viruses
DNA Both Both Both Both Both Both
Obligate intracellular pathogen No No Yes Yes Maybe Yes
Peptidoglycan cellwall Yes No Yes (1 stage) Yes No No
Growth on artifical media Yes Yes No No Yes No
Contain ribosomes Yes Yes Yes Yes Yes No

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This page was last modified on 16 March 2008, at 20:05.
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