Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

An Introduction to the Viruses


Published on

  • God bless Dr Climent for his marvelous work in my life, I was suffering for Herpes since since 2010 and I was taking my medications and i wasn't satisfied i needed to get the Herpes out of my body, I searched about some possible cure for Herpes and i saw a comment about Dr climent, how he cured a woman with his herbal medicine, I contacted him and he guided me. I asked for solutions, he started the remedy for my health, he sent me the medicine through UPS his email. Please contact him for help TYPES OF CURES HSV 1&2 LASER FIVER KIDNEY DISEASE HEART DISEASE CANCER GONORRHEA STD HERBAL REMEDY FOR PREGNANCY or call +2347036879479 +2347036879479
    Are you sure you want to  Yes  No
    Your message goes here

An Introduction to the Viruses

  1. 1. Foundations in Microbiology Chapter 6 PowerPoint to accompany Fifth Edition Talaro Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  2. 2. An Introduction to the Viruses Chapter 6
  3. 4. Size of viruses
  4. 5. Naming viruses <ul><li>No taxa above Family (no kingdom, phylum, etc) </li></ul><ul><li>19 families of animal viruses </li></ul><ul><li>Family name ends in -viridae , Herpesviridae </li></ul><ul><li>Genus name ends in -virus, Simplexvirus </li></ul><ul><li>Herpes simplex virus I (HSV-I) </li></ul>
  5. 6. <ul><li>Family – Herpesviridae </li></ul><ul><li>Genus – Varicellovirus </li></ul><ul><li>Common name – chickenpox virus </li></ul><ul><li>Disease - chickenpox </li></ul>
  6. 7. capsids <ul><li>All viruses have capsids- protein coats that enclose & protect their nucleic acid </li></ul><ul><li>Each capsid is constructed from identical subunits called capsomers made of protein </li></ul><ul><li>2 types: </li></ul><ul><ul><li>helical </li></ul></ul><ul><ul><li>iscosahedral </li></ul></ul>
  7. 8. helical
  8. 9. icosahedral
  9. 10. icosahedral <ul><li>20-sided with 12 corners </li></ul><ul><li>Vary in the number of capsomers </li></ul><ul><li>Each capsomer may be made of 1 or several proteins </li></ul><ul><li>Some are enveloped </li></ul>
  10. 11. complex Fig 6.9a,c
  11. 12. 6 steps in phage replication <ul><li>adsorption – binding of virus to specific molecule on host cell </li></ul><ul><li>penetration –genome enters host cell </li></ul><ul><li>replication – viral components produced </li></ul><ul><li>assembly - viral components assembled </li></ul><ul><li>maturation – completion of viral formation </li></ul><ul><li>release – viruses leave cell to infect other cells </li></ul>
  12. 13. Fig 6.11
  13. 14. penetration
  14. 15. Bacteriophage assembly line
  15. 16. <ul><li>Not all bacteriophages lyse cells </li></ul><ul><li>Temperate phages insert their viral DNA into the host chromosome & viral replication stops at there until some later time. </li></ul><ul><li>Lysogeny - bacterial chromosome carries phage DNA </li></ul>
  16. 17. Host range <ul><li>Spectrum of cells a virus can infect </li></ul><ul><ul><li>cell has to have a specific structure (receptor) on its surface for viral attachment </li></ul></ul><ul><ul><li>cell has to contain all of the enzymes and materials needed to produce new virions </li></ul></ul><ul><li>May be one species or many </li></ul><ul><ul><li>HIV (only humans) vs rabies (many animals) </li></ul></ul><ul><li>May be one tissue or many within a host </li></ul><ul><ul><li>Hepatitis (liver) vs polio (intestinal & nerve cells) </li></ul></ul>
  17. 18. Differences between phage and animal virus replication <ul><li>Animal virus replication is more complex than phage replication because host cells are more complex. </li></ul><ul><li>Animal viruses cannot inject their DNA. </li></ul><ul><li>Lysogeny for phage, latency for animal viruses </li></ul>
  18. 19. Animal virus replication <ul><li>adsorption </li></ul><ul><li>penetration/uncoating of genome </li></ul><ul><li>duplication/synthesis </li></ul><ul><li>assembly </li></ul><ul><li>release </li></ul>
  19. 21. adsorption
  20. 22. penetration
  21. 23. Release by budding
  22. 24. Cytopathic effects- virus-induced damage to cells <ul><li>changes in size & shape </li></ul><ul><li>cytoplasmic inclusion bodies </li></ul><ul><li>nuclear inclusion bodies </li></ul><ul><li>cells fuse to form multinucleated cells </li></ul><ul><li>cell lysis </li></ul><ul><li>alter DNA </li></ul><ul><li>transform cells into cancerous cells </li></ul>
  23. 25. Cytopathic changes in cells
  24. 26. How do we grow viruses? Obligate intracellular parasites require appropriate cells to replicate.
  25. 27. Growing animal viruses <ul><li>live animals </li></ul><ul><li>bird embryos – chicken, duck; intact, self-supporting unit, sterile, self-nourished </li></ul><ul><li>cell culture </li></ul>
  26. 30. Other noncellular infectious agents <ul><li>prions - misfolded proteins, contain no nucleic acid </li></ul><ul><ul><li>cause spongiform encephalopathies – holes in the brain </li></ul></ul><ul><ul><li>common in animals </li></ul></ul><ul><ul><ul><li>scrapie in sheep & goats </li></ul></ul></ul><ul><ul><ul><li>bovine spongiform encephalopathies (BSE), aka mad cow disease </li></ul></ul></ul><ul><ul><ul><li>humans – Creutzfeldt-Jakob Disease </li></ul></ul></ul><ul><li>viroids - short pieces of RNA, no protein coat </li></ul><ul><ul><li>only been identified in plants, so far </li></ul></ul>
  27. 31. Diagnosis of viral diseases <ul><li>More difficult than other agents </li></ul><ul><li>Consider overall clinical picture </li></ul><ul><li>Take appropriate sample </li></ul><ul><ul><li>Infect cell culture- look for characteristic cytopathic effects </li></ul></ul><ul><ul><li>Screen for parts of the virus </li></ul></ul><ul><ul><li>Screen for immune response to virus (antibodies) </li></ul></ul>
  28. 32. diagnosis