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Ch. 7 - Sect. 1- VIRUSES
images3.jpgVIRUSES ARE NOT LIVING ORGANISMS BECAUSE. . .

1) They are not composed of one or more cells.
2) They do not grow and metabolize.
3) Most do not move on their own.
4) They can only reproduce with the help of a HOST organism's cells.


Essentially, they are microscopic biological infectious agents (entities, particles) that can replicate only inside the living cells of organisms. The most basic of viruses are a nucleic acid (RNA or DNA) surrounded by a protective protein coat.
More complex viruses have an even further protein covering and outer protein antigens present on that covering.

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ANATOMY OF A VIRUS
All viruses follow the basic prototype of having a nucleic acid in the center covered in a protein coat. Some are very complicated, others more basic.


VIRAL TRANSMISSION
1) CONTACT
2) ATTACHMENT
3) PENETRATION / UNCOATING
4) REPLICATION & ASSEMBLY
5) RELEASE



VIRUS CYCLES OF INFECTION ( http://www.cbu.edu/~seisen/Viruses.htm): THE LYTIC CYCLE vs. THE LYSOGENIC CYCLE

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In the lytic cycle (left), the virus reproduces itself using the host cell's chemical machinery. The red spiral lines in the drawing indicate the virus's genetic material. The orange portion is the outer shell that protects it.
Regardless of the type of host cell, all viruses follow the same basic steps in what is known as the lytic cycle (see figure above):
  1. A virus particle attaches to a host cell.
  2. The particle releases its genetic instructions into the host cell.
  3. The injected genetic material recruits the host cell's enzymes.
  4. The enzymes make parts for more new virus particles.
  5. The new particles assemble the parts into new viruses.
  6. The new particles break free (by pinching out/budding or by lysing the cell membrane) from the host cell.


All viruses have some type of protein on the outside coat or envelope that "feels" or "recognizes" the proper host cell(s). This protein attaches the virus to the membrane of the host cell. Some enveloped viruses can dissolve right through the cell membrane of the host because both the virus envelope and the cell membrane are made of lipids.
Those viruses that do not enter the cell must inject their contents (genetic instructions, enzymes) into the host cell. Those viruses that dissolve into a cell simply release their contents once inside the host. In either case, the results are the same.





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Lysogenic Cycle

Once inside the host cell, some viruses, such as herpes and HIV, do not reproduce right away. Instead, they mix their genetic instructions into the host cell's genetic instructions. When the host cell reproduces, the viral genetic instructions get copied into the host cell's offspring. The host cells may undergo many rounds of reproduction, and then some environmental or predetermined genetic signal will stir the "sleeping" viral instructions. The viral genetic instructions will then take over the host's machinery and make new viruses as described above. This cycle, called the lysogenic cycle, is shown in the figure below.

In the lysogenic cycle (right), the virus reproduces by first injecting its genetic material, indicated by the red line, into the host cell's genetic instructions.
Because a virus is merely a set of genetic instructions surrounded by a protein coat, and because it does not carry out any biochemical reactions of its own, viruses can live for years or longer outside a host cell. Some viruses can "sleep" inside the genetic instructions of the host cells for years before reproducing. For example, a person infected with HIV can live without showing symptoms of AIDS for years, but they can still spread the virus to others.






UNDERSTANDING VIRUSES

HOW VACCINES WORK
http://www.historyofvaccines.org/content/how-vaccines-work
how_vaccines_work.jpg


HOW VACCINES ARE MADE
http://www.historyofvaccines.org/content/how-vaccines-are-made
making_vaccine.jpg


TYPES OF VACCINES
http://www.historyofvaccines.org/content/types-vaccines
influenza_virus_types.jpg

KOCH'S POSTULATES
http://www.historyofvaccines.org/content/koch%E2%80%99s-postulates
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HERD IMMUNITY
http://www.historyofvaccines.org/content/herd-immunity-0
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HISTORY OF VACCINES
http://www.historyofvaccines.org/content/pioneer-breakthroughs
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This cartoon is just one example of the mockery that some people made of medicine in the 18th and 19th centuries. The smallpox vaccine, originally prepared from the lesions of people infected with cowpox (a much milder disease contracted from cows), made many people fearful -- of cow-borne disease, of usurping God's will, of the unknown. This 1802 cartoon shows Edward Jenner, the vaccine's discoverer, administering it, as previous vaccine recipients erupt with cow-like features.



























Play illsville:http://www.historyofvaccines.org/content/illsville-fight-disease









Virus Article Jigsaw Exercise

Read the article assigned to you and pair with others who have also read it to discuss the content. Then get together in groups where everyone has read a different article and share what you learned.

Article 1) http://www.livescience.com/8618-kids-exposed-strain-cold-virus-obese.html

Article 2) http://www.livescience.com/10023-viruses-cancer-previously-thought.html

Article 3) http://www.livescience.com/8422-bat-rabies-hops-species-expected.html

Article 4) http://www.livescience.com/7934-frigid-antarctica-loaded-viruses.html



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Ch. 7, Sect. 2: BACTERIA - ARCHAEBACTERIA & EUBACTERIA KINGDOMS1997-04-14.gif
KEY THEMES:
1. HOW DO PROKARYOTES DIFFER FROM EUKARYOTES?
2. HOW DO THE 2 KINGDOMS OF BACTERIA COMPARE?
3. HOW ARE BACTERIA CLASSIFIED IN MICROBIOLOGY (GRAM STAIN + or -; COLONY SHAPE & COLOR; CELL SHAPE AND ORGANIZATION)?
4. HOW DO BACTERIA REPRODUCE?
5. HOW ARE MICROBES HELPFUL AND HARMFUL AMONG HUMAN CIVILIZATION?


LINKS:
http://www.pbs.org/wgbh/nova/body/killer-microbe.html
http://www.pbs.org/wgbh/nova/military/anthrax-investigation.html
http://www.pbs.org/wgbh/nova/tech/putting-bacteria-to-work.html
http://www.cellsalive.com/toc_micro.htm



PROKARYOTES

1) cell walls
gram positive vs. gram negative

http://learn.chm.msu.edu/vibl/content/gramstain.html

Gram_positive_cell_wall_Gram_negative_cell_wall.jpg


2) obtaining energy
autotrophic vs. heterotrophic
chemosynthesis.jpg



3) reproduction
asexual (binary fission) vs. sexual (conjugation); endopsore formation
binary_fission_jpg.jpg Bacterial_Conjugation_1.jpg
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http://learn.chm.msu.edu/vibl/content/streakplate.html

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**CASE STUDIES IN PATHOGENIC MICROBIOLOGY**

case 1

case 2

case 3

case 4

case 5

case 6

case 7

case 8