1. Acellular Particles: Viruses, Prions, and Viroids nonliving infectious agents
Bacteria are cells – self-sufficient, reproduce and grow independently. Alive!

2. Virus Pros and Cons: Pros: Cons
Infect and kill bacteria that makes humans sick (bacteriophages are viruses that attack bacteria)
Used in gene therapy to deliver helpful genes to target cells
Cons
Cause many serious human diseases from rabies to HIV to chicken pox…..

3. What is a virus?
They are obligate intracellular parasites - not technically alive
They contain either RNA (retrovirus) or DNA –and not much else!
The have a protein coating called a capsid and can contain lipids.
They take over the metabolic capabilities of cells in order to replicate and evolve (SARS). Cannot replicate on their own.
Viruses are derived from their hosts and are more closely related to them, than to each other.
One virus called a ‘virion’
Cause disease in animals, plants, and bacteria but also transfer genetic information (horizontal gene transfer) and increase genetic diversity in their hosts
Viruses are highly specific – their surface proteins must match the membrane proteins of their host cell in order for them to invade

5. How do viruses replicate?
Viruses replicate two different ways.
Lytic viruses invade cells and use the cell’s machinery to make more viruses immediately. The host cells “lyse” or burst (and die) and the new viruses emerge to invade new cells.
The common cold is a good example.
Think of an outlaw taking over a town in the wild west – fast, violent, take no hostages approach. Or a hostile takeover….

7. Viral replication continued
Lysogenic viruses keep their hosts alive for a while. In lysogeny, the virus is able to combine it’s genetic material with that of the host. Its genetic material is replicated whenever the cell divides and replicates its own genetic material.
Can stay inactive in cell for a long time, and then reactivate….and become lytic.
Often the host cell will demonstrate notable differences (phage conversion). (For example, diptheria, cholera, botulism are bacteria that only produce lethal toxins when infected by a bacteriophage. )
Vibrio cholerae
Corynebacterium diptheriae
Clostridium botulinim

8. http://www. phschool. com/webcodes10/index. cfm

9. Vaccines
Vaccine = artificially acquired immunity – both viral and bacterial vaccines
Use dead, weakened or slightly different pathogen to stimulate body to to create antibodies to a disease…..antibodies then stored in our bodies in case of future exposure….
Lady Montague 1720’s brought vaccine idea from Turkey to England – Middle East far ahead of Europe on this
Edward Jenner 1790’s cow pox vs. small pox
Vacca = Vache = cow
1980 the WHO announced the eradication of small pox. The last case was in Stored at CDC and a Russian lab just in case……

10. Prions and Viroids Viriods are “naked” RNA; hitchhike inside viruses
Prions are parts of a protein. Smallest of the acellular particles
Prions cause host organism’s brain proteins to misfold, which causes brain degeneration.
Mad Cow Disease, Sheep scrapie, Creutzfeldt-Jakob Disease, (9 total)
All cause nuerological disease called spongiform encephalopathies (large holes in the brain)
Very poorly understood – how can something be infectious and replicate with no genetic material??
Still some controversy about whether they cause disease or are a symptom of it….
Viriods are “naked” RNA; hitchhike inside viruses
Cause disease by gene silencing – turn off host cell’s genes
Found mostly in plants
Only one human disease caused by a viroid: hepatitis D