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Viruses

Viruses. Latin : Poison – slippery toxin. Virus Video. http://www.youtube.com/watch?v=L8oHs7G_syI&list=PL7A750281106CD067&index=22. Size comparisons. What are Viruses?. Smaller and simpler than bacteria NOT made up of cells

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Viruses

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  1. Viruses Latin: Poison – slippery toxin

  2. Virus Video http://www.youtube.com/watch?v=L8oHs7G_syI&list=PL7A750281106CD067&index=22

  3. Size comparisons

  4. What are Viruses? • Smaller and simpler than bacteria • NOT made up of cells • Lack most metabolic machinery, so must hijack a cell to reproduce • Are little more than a combination of nucleic acid and protein –“genes” in a protein coat • *Viruses are NOT considered ‘living things’

  5. Viral Structure • 2 parts: • Capsid– protein “coat” • Accessory structures that aid in host infection: • Viral envelopes- cloak capsid; derived from host’s membrane • Glycoproteins act as anchoring “spikes” • “Tail” act as hypodermic syringe • Nucleic Acid • Genome • DNA or RNA

  6. Common Viruses • Flu Virus • HIV: Retrovirus • Herpes Simplex I • Chicken pox virus (shingles) • West Nile Virus: most people infected never know they have it! Flu Virus

  7. Figure 18.02x2 Phages

  8. H1N1 Invading Lung Cells

  9. ClassificationViral Genomes = Classification • 4 Types • 1. Double Strand DNA • 2. Single Strand DNA • 3. Double Strand RNA • 4. Single Strand RNA • Classified “DNA-like or RNA-like/Retrovirus” • Further naming is based on surface proteins • H1N1 – H proteins = hemoggluttin, N = neuraminidase

  10. Viral reproductive cycle (Infection) - Overview • Virus uses host’s machinery to replicate viral genome • Host’s machinery used to make capsid proteins • Use transcription and translation. • New viral genomes and capsids are assembled into new viruses

  11. What is a good analogy for viral infection?

  12. Lytic vs. Lysogenic Cycles • Lytic cycle -virus takes over the host cell immediately and reproduces quickly • Virulent infections – quick! • Infections you “get over” • Ex. Cold virus, influenza • Lysogenic cycle - virus “hides” in host’s DNA until optimal conditions for viral survival are present • Lifetime Infections • Ex. HIV, herpes

  13. 5 Steps of Lytic Cycle • 1. Attachment – “lock and key” • 2. Penetration – “genome injection” • 3. Genome Replication and Synthesis - “hijack host machinery” • 4. Assembly - “hijack host energy” • 5. Lysis (Release) – “burst free”

  14. Lytic Virus Lytic Bacteriophage

  15. 8 steps of the Lysogenic Cycle • Attachment • Penetration • Integration into the host’s DNA (provirus) • Replication of cells (including virus DNA) through mitosis • Trigger – stress, chemicals • Replication & Synthesis of Virus • Assembly • Lysis

  16. Lysogenic Virus Prophage infection

  17. Ex: Lysogenic CycleHerpsevirus in Humans • Herpesviruses – genomes of double-stranded DNA • Reproduce within the cell nucleus • Hides in cell DNA – replicated during mitosis • Infections tend to recur throughout life in times of stress  viruses will emerge from thousands of cells then

  18. Figure 18.5 The lysogenic and lytic reproductive cycles of phage , a temperate phage

  19. RNA Viruses and Retroviruses • These viruses have a HIGH MUTATION RATE • There is no good PROOFREADING mechanism like there is when going from DNA to RNA • These means there are many different STRAINS of RNA viruses and Retroviruses • Makes VACCINES very difficult to develop

  20. The Red Queen Hypothesis • Evolution “runs around” to stay in the “same place” • Disease/Host – HIV = fastest “evolving” thing on planet! • Lysogenic viruses ALWAYS under selective pressure – mutations selected for • In 10 years an HIV infection will be up to 60% different in RNA bases than the original strain

  21. Emerging/Zoonotic Viruses • Host range is specific – lock & key • Sometimes virus can mutate & be able to “change hosts” • Evolution • Zoonotic Virus – from different animal host • Usually severe – immunity? • Ex: Ebola, Hendra, Swine Flu

  22. Why not antibiotics? • Antibiotics target cellular properties • Cell wall of bacteria • Antibiotics target life processes • DNA replication • Protein Synthesis • Nyquil? Robitussin? Tylenol Cold? • Immune System • Destroys viruses physically or rids body of them - antibodies • Keeps lysogenic “hidden” in genome • Antiviral medicines • Prevent HOST cells from life processes • DNA replication or Protein Synthesis • Ex: Abreva, AZT

  23. Differences Between Bacteria and Viruses • Bacteria are classified as living • Bacteria are prokaryotic cells • No Nucleus • Bacteria can perform metabolic functions • Replication • Protein Synthesis • Use and obtain own energy in various ways • Move on their own Viruses are not affected by antibiotics

  24. Vaccines: the war against the virus • Prevention • Injecting WEAKENED or “HEAT KILLED” virus particles to cause your immune system to recognize the virus quickly • Immune cells can recognize SHAPE of capsid or DNA/RNA markers • Create antibodies (Memory cells – B & T cells) • When in contact with the real virus, your IMMUNE SYSTEM should recognize the virus and come to the rescue

  25. Vaccine contributors • Edward Jenner did early, important work using cowpox and smallpox viruses. He used cowpox to stimulate an immune response to the very similar smallpox virus • Jenner tried out an early small pox vaccine using his SON in 1796

  26. Vaccine contributors • Jonas Salk “killed” the polio virus but kept enough of it intact (protein capsid) so that they body could recognize the actual virus following exposure to the killed form. • Albert Sabin felt that a weakened, “live” form would be more effective (mutated DNA) It is now the vaccine of choice, in part because it is actually cheaper and easier to make. The Sabin vaccine can cause polio in persons with a compromised immune system.

  27. Is this correct?!?! • Kills 99.99% of “germs”

  28. Terms to know: • Temperate: when the virus is dormant or inactive • Virulent: when a virus is active • Pathogenic: disease causing • Epidemic • Pandemic

  29. Viruses – Going Further • Oncogenic Viruses – Lysogenic viruses that can lead to cancers; insertion of viral genome mutates host genome  Cancer • HPV, Rouse Sarcoma • Why we have the Guardasil Vaccine • Prions – Infectious protein particles that can change the shape (conformation) of normal proteins in the body • Mad Cow Disease, Crutzfield-Jacob disease

  30. The Amazing World of Bacteria Bacteria on the point of a pin!!! Electron Microscope 1500 x

  31. https://www.youtube.com/watch?v=vAR47-g6tlA&list=PL3EED4C1D684D3ADF&index=36https://www.youtube.com/watch?v=vAR47-g6tlA&list=PL3EED4C1D684D3ADF&index=36

  32. Differences Between Bacteria and Viruses Virus • Non-Living • Cannot perform metabolic functions • Some - no DNA • Cannot move • Cannot reproduce without a host • Not classified Bacteria Living Prokaryotes DNA Metabolic functions: replication, protein synthesis, use and obtain own energy Move Reproduce Classified

  33. Differences between Prokaryotes and Eukaryotes • Prokaryotes • No nucleus or membrane-bound organelles • Unicellular only • Eukaryotes are not AS affected by most antibiotics • difference in cell wall • metabolism • Prokaryotes - extreme environments • most eukaryotes can’t tolerate • Fun Fact – there are more prokaryotes in a hand full of dirt (or cup full of sea water) than humans that have ever lived!!!

  34. 2 Kingdoms of Bacteria • Eubacteria – • Peptidoglycan in cell wall • Affected by antibiotics • Archaebacteria – “Ancient Bacteria”; • Extreme Environments • no peptidoglycan in cell wall • not affected by antibiotics • 3 Domain system - early divergence of 2 bacteria types • Archaea and Bacteria • We will focus on Bacteria (Eubacteria)

  35. Typical Prokaryotic Structure

  36. Movement • Flagella – help propel the cell • On outside of cell wall • Scattered all over surface or concentrated at the ends • Cilia – hair-like projections outside cell • Slime – oozes from cell • helps bacteria glide along

  37. Flagella

  38. Cell Wall • 2 different types in Eubacteria • Peptidoglycan on outside layer • Lipid carbohydrate layer over peptidoglycan layer • Antibiotics target mainly peptidoglycan in cell wall • To determine cell wall structure, use Gram Stain: • Gram (+) means peptidoglycan in outer wall - purple • Gram (-) means outer layer of lipid/carb covers peptidoglycan layer- pink/red • Antibiotics mainly kill Gram (+) bacteria

  39. Mix of Gram(+) and (-) Bacteria

  40. Endospore – Bacterial Protection Phase • If growth conditions are not suitable for bacteria: • It grows a thick wall of keratin protein around cell wall • Protects • Can remain dormantindefinitely • Can grow once conditions return to favorable • Why we must autoclave

  41. Naming bacteria – shape and colony type • Unicellular • may aggregate in groups of two or more • True colonies – permanent groups of identical cells – *chains (strepto) *clusters (staphalo) • Differ in shape – 3 most common *spherical (coccus or cocci) *rod-like (bacillus or bacilli) *helical (spirillum or spirilla, spirochetes) • Diameter ranges between 1-5 um; largest is .75 mm in diameter

  42. Draw these shapes in your notes and know their names!!! Cocci Bacillus Spirillum

  43. Modes of Nutrition: Very Diverse • Nutrition of prokaryotes – how org obtains energy and a carbon source to build org molecules • 4 categories: 1. photoautotrophs – use light to make food 2. chemoautotrophs – need CO2 as carbon source, and get chemical energy from inorganic substances 3. photoheterotrophs – use light to make energy, but need a carbon source to start with 4. chemoheterotrophs – must “eat” other organisms to get food in chemical form most bacteria are this type • Saprobes – decomposing bacteria • Parasites – infectious bacteria

  44. Reproduction: Binary Fission • Asexual Reproduction - No recombination of genetic material! • Bacterial cell just splits in half and have two cells from the original • *Conjugation – bacteria can swap plasmids (2nd genome) • Primitive sexual reproduction?

  45. Prokaryotes are not all bad… • Many do cause disease, but others are symbiotic (E. coli in intestines), help with cycling nutrients (decomposers and carbon cycle) • Many are important in food processing (yogurt, cheese, etc) • Are about 5,000 species known, could be as many as 4 million

  46. Ecological Impact of Prokaryotes • Recycling of nutrients (decomposers) • Symbiotic relationships • Cause many Diseases • opportunistic • Bioremediation – use or orgs to remove pollutants Ex. Sewage treatment plants – anaerobic prok Ex. Decompose petroleum compounds at oil spills -- pseudomonads • Act as metabolic factories for human use -produce acetone, butanol -make vitamins, antibiotics -food flavorings (yogurt, cheese) -DNA technology – produce hormones like insulin

  47. Preventing bacterial infection • Sterilization of surfaces (with antiseptics, heat, or steam) • Cooling, freezing food • Dehydrating food (salt curing) • Use chemical preservatives (food or water – chlorine) • Radiation • Pasteurization (heating liquids) • Canning • Washing hands!!! *Antibiotics are used only AFTER have infection present

  48. Antibiotics vs. Antibodies vs. Antiseptics • Antibodies – produced by white blood cells in the body (internal line of defense) - can use vaccines • Antibiotics – kill bacteria using chemicals that are specific to bacteria metabolism and structure *introduced IN TO body or *ON TO site of infection as surface medication • Antiseptics - Kill bacteria on OUTSIDE of body or on membranes that line areas leading to inside (ex. Mouth) Ex. Alcohol, Listerine, Iodine, Hydrogen Peroxide *Disinfectants – destroy bacteria/viruses on non-living surfaces Ex: chlorox, bleach, lysol

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