1. Viruses and Bacteria

2. What is a virus? DNA or RNA enclosed in a protein coat
A parasite of an organism
Non-living: not made of cells, unable to reproduce, feed, do not die
Human AIDS virus

3. Virus Structure Protein coat (capsid) contains the DNA or RNA
It attaches to and tricks its host cell into letting it inside
Once inside the viral DNA or RNA takes over

4. How do Viruses Reproduce?
Lytic Infection
Virus enters cell
Host cell is directed to copy the viral DNA
Cell bursts open releasing new viruses
Examples: flu, cold,
Lysogenic Infection
Virus enters cell
Virus attaches to host DNA
Replication of host and viral DNA
Cell does not burst right away
Eventually becomes lytic
Examples: HIV, retroviruses

5. What are Bacteria? Simplest living things Single celled prokaryotes
No nucleus or other membrane-bound organelles
Three basic shapes
Can be arranged in clusters (staphylo-) or chains (strepto-)

6. Bacteria Structure Cell wall made of peptidoglycan Cell membrane
Ribosomes
Some have flagella to move through water
Many do not move

7. Some Bacteria are Dangerous
Diseases
Cholera
Tuberculosis
Tetanus
Salmonella food poisoning
Botulism
Staphylococcus infections of skin
A soldier dying of tetanus
(Painting by Sir Charles Bell)

8. Most Bacteria are Helpful
Important uses of Bacteria
Recycling nutrients (decomposers)
Nitrogen fixers
Making certain foods
Cheese, sour cream, butter, vinegar

9. Cheese facts… Cheese came into being in prehistoric times.
Must have resulted from the simple observation that milk left in a container ends up by coagulating, even more if it is hot.
differentiated by:
the type of milk - raw, skimmed or pasteurized
by the animal - cow, goat, sheep, buffalo, horse or camel.