Notes from 0ctober 30th for Microbiology

Microbiology October 30, 2009. A lecture on viruses in three acts
I. Ground zero.
a. Chapter 1: Doctrix Robson’s Checkered Past
b. Chapter 2: Viral replication
• Need a host cell to replicate
• Because viruses need a host cell to copy genome, not quite alive
1. Virus attaches to host cell – interaction between specific proteins on host cell surface and viral protein allow this.
i. Bacteriophage capsid (protein outside of a virus that has all DNA on the inside) stays on outside of host cell, DNA injected into cell.
- Caspid = protein shell surrounding viral genome
ii. Viruses of eukaryotic cells: Virus engulfed by host cell; caspid broken down y our enzymes, which in return, frees the genetic material of virus (viral genomes can be DNA or RNA)
2. Viral genes expressed (i.e., genetic material of virus transcribed and translated into protein) by host cell ribosomes, etc. and viral genetic material copied by host cell enzymes (DNA polymerase, etc.)
3. New viral genetic material (copied) packaged into new capsid proteins  new virus particles!
- Some viruses DNA or RNA of Virus alone, in cell  new functional viruses
4. Viruses released from host cell
- Eukaryotes: viruses often “bud” (new virus uses capsid protein to wrap itself in the eukaryotic membrane and turns and tears piece of leaving a small enough hole the cell can repair itself) off of host cell  not necessarily fatal to host cell but viral infection does keep cell from doing its job – can  death (ex. HIV) (while kept alive are prevented from performing the job they need to be doing)
c. Chapter 3: Viral affinity for host cells
• viral interaction with host cell proteins very specific so specific viruses can only infect specific cells
• Herpes Simplex 1: cold sore virus
 Infect epithelial cells and neurons
II. The Curious Case of Dr. Wimmer
a. Chapter 1: Host cells, host species, and the potential for potential for disease eradication
b. Chapter 2: Polio
• RNA genome
• Can only infect intestinal epithelial cells and Neurons and only infect the cells in humans in nature
• Eradication: destroy disease, so never infects again
• Good candidates for eradication:
- Viral disease that only infect humans and have reliable vaccine against
- Can never be eradicated because can be grown with simple chemistry
c. Chapter 3: Viral synthesis
III. Death Rides a Pied Horse
a. Chapter 1: The pox
• Small pox: only infects human epithelial cells. Covers victim with rapidly spreading blisters. Blisters burst. After a few weeks skin sluffs of or you get better. Smallpox Mortality rate: experience population30% naive population 90%
• Vaccine kills 1 in a million people. Get vaccine swells puss filled blister, scabs over and the scab falls off. After a month or two looks like normal scar tissue
• Small pox cases have decreased rapidly. 1977 small pox has been wiped of the face of the earth
• One problem. The Soviet Union and United states did not want to play along with Smallpox eradication. Both insisted that if they go along with eradication that we would be allowed to keep a few viles of small pox so that we could hit the back and hit them hard.
• United States viles are under lock and key. After fall of Soviet Union the viles disappeared. No one knows where they Soviets vile went. No experienced population is on the earth anymore.
b. Chapter 2: Hope springs eternal
c. Chapter 3: Victory
d. Chapter 4: tragedy
e. Chapter 5: The End?

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