Lunchtime!!

1. Lunchtime!! T4 Bacteriophages

2. T4 Bacteriophage • Bacteriophage – virus that attacks bacteria • Attacks Escherichia Coli bacteria • Injects its DNA into the bacterium’s DNA • Virus takes over the bacterium’s genetic mechanism • Called an obligate intracellular parasite • Obligate – only exists in certain cases • Intracellular – Internal or inside cell • Parasite – lives off another organism

3. Viral Structure • The smallest viruses are 20nm in diameter, smaller than a ribosome • What does a ribosome do? • What does that mean for its size relative to an animal cell?

4. Who’s bigger?

5. Let’s talk about viruses #1 • 1. HIV/AIDS • In 2007, 33.2 million with HIV/AIDS • 2.1 million fatalities from HIV • 68% of infections are in Sub-Saharan Africa • 2.5 million new infections in 2006 • Retrovirus

6. Viral Images

7. Let’s talk about viruses #2 • 2. Influenza • 7th leading cause of death worldwide, but not in the US • Causes widespread pandemics every decade or so • Fatality is more likely in the elderly & infants • Avian influenza in the 1990’s was the last major pandemic

8. Let’s talk about viruses #3 • 3. Ebola Hemorrhagic Virus • “Occasionally, Internal and external hemorrhage from orifices, such as the nose and mouth may also occur, as well as from incompletely healed injuries such as needle-puncture sites.” • Mortality rates are generally high, ranging from 50% - 90% • Ebola is referred to as a “slate wiper” due to its remarkably high case fatality rate

9. Ebola outbreak in Congo

10. Are Viruses alive? • They have DNA (or RNA) • They are not able to reproduce on their own • They infect other cells in order to perpetuate their life cycle • Viruses can be crystallized, but no other cells can be crystallized • May contain a membranous envelope

11. Viral Genomes • Basically – nucleic acid with a protein coat • Some will have DNA (2-strands or 1-strand) • Papillomavirus, Herpesvirus, & Smallpox • Parvovirus (1-strand) • Others have RNA (2 or 1 strand again) • HIV, Influenza & Ebola • Amount of genes also varies widely depending on the virus

12. Capsids & Envelopes • Capsid – Protein shell enclosing the viral genome • Rod-shaped, polyhedral, or more complicated (T4) • Capsids are built from protein subunits called capsomeres • Envelope – Helps viruses infect their hosts • Derived from the membranes of the host cell • Host phospholipids & membrane proteins

13. Viral Life Cycle Animation(s) • 19_04SimpViralReproCycle

14. Simple Viral Reproductive Cycle

15. 2 Types of Viral Life cycles • Lytic • Virulent cycle • Results in death of host cell • New phages are produced, host cell wall destroyed, and progeny (daughter viruses) are released to infect other cells • Lysogenic • Viral DNA is incorporated into host DNA • This viral DNA is called prophage (provirus in euks.) • Infection silently spreads to daughter cells

16. Lytic Cycle Animation • 19_05PhageT4LyticCycle

17. Lytic Cycle

18. Lytic vs. Lysogenic Cycle • 19_06LysogenicLyticCycle

19. Lytic vs. Lysogenic Cycle

20. HIV Life Cycle • 19_08HIVReproCycle

22. Viroids & Prions • Viroids • Just RNA • Significantly smaller than viruses • Infect plants • Prions • Proteins that are capable of infecting cells • No DNA or RNA • Causes degenerative brain diseases • CJD (Creutzfeldt-Jacobs disease V1) • Bovine Spongiform Encephalopathy (BSE)

23. Prions & Alzheimer's • Prions form into incorrect shape in CJD, but not so in Alzheimer • Prions interact with plaques to allows the plaques to damage brain cells • Amyloid-beta is the go between • Mechanism of prion and amyloid-beta is unknown • But sci. know there is an interaction, and this interaction = Alzheimers • Possible treatment avenue