1. Viruses SBI 3C – Grade 11 College Biology

2. Bacteria vs. Viruses Let’s investigate! http://learn.genetics.utah.edu/content/begin/cells/scale/ E. coli O157:H7 Responsible for 1% of food borne illness Causes bloody diarrhea Can be lethal Antibiotic resistant ……….but not T4 Phage resistant!

3. Bacteria vs. Viruses Viruses (“poison”) Intracellular Parasite Host specific Bacteriophage (“Bacteria Eater”) – viruses specific to infecting bacteria Phage T4 Head Protein Sheath Tail Fibers

4. Virus Types Characterized by: 1.Genome: DNA or RNA, Single Stranded or Double Stranded, Linear or Circular 2.Capsid or Envelope

5. Virus Sizes T4 Genome Size

6. Virus Attachment E. coli O157:H7

7. Viral Penetration & Uncoating (disassembly) E. coli O157:H7 1 min - Host DNA, RNA and protein synthesis is turned off

8. Viral Transcription & Translation E. coli O157:H7 2 min – viral mRNA synthesis begins 3 min – bacterial DNA begins to breakdown

9. Viral Assembly E. coli O157:H7 5 min – Phage DNA synthesized 12 min – completed heads and tails appear

10. Viral Assembly E. coli O157:H7 15 min – complete Phage particles appear

11. Bacterial Lysis: 100-300 Phages Released E. coli O157:H7 22 min – cell lysis and Phage release

12. Viral Replication Summary Step 1 – A&P: Attachment & Penetration Step 2 – U: Uncoating – viral nucleic acid available for transcription Step 3 – R: Replication of Phage DNA & protein synthesis Step 4 – A&R: Assembly & Release

13. Viral Lytic Cycle vs Lysogenic

14. 22 minutes?! – How do we know? http://www.youtube.com/watch?v=zGSSDJhHgp0&NR=1 French-Canadian Microbiologist First to see bacteriophage lysis E. coli in 1917 Phage therapy was a successful method of treatment until 1928 …….Why??? Felix d’Herelle

15. Virus History 1200 B.C. Pharaoh Siptah had Polio 1151 B.C. Ramses V died – his sarcophagus shows pockmarks from Smallpox virus 1892 A.D. Viruses first identified in Tobacco *First time the word “virus” used

16. Virus Evolution Theory – evolved from host genome during genetic events (e.g. genetic mutations, genome rearrangement, gene acquisition, creation, deletion, as well as recombination and translation events) Co-evolve with host ……..but must be faster than the host Needs a host to survive, but beneficial to cross-over to a new host (e.g. animal virus into human) Some viruses overcome host immune memory by mutating to re- infect its host ……..RNA viruses are good at this e.g. HIV mutates so fast the immune system can never clear itself from the body so vaccines end-up failing

17. LivingNon-living ReplicateNo metabolism EvolveNo respiration Need a host to survive Does it really matter??? Viruses: What do we need to know?

18. Method of Transmission Method of Prevention

19. Viruses: What do we need to know? Antiviral Drugs – target viruses at various stages in replication (A&P, U, R or A&R) Phage Therapy – back on the rise as an alternative to antibiotics and in treating plant-based bacterial diseases

20. SBI 3C - Viruses Presented By Joyce Longfield