1. Viruses & Bacteria

2. What Do You Already Know?
What are the differences between bacteria and viruses?
Are all bacteria harmful?
Are bacteria and viruses living?
If you have a cold, should you take an antibiotic? Why or why not?
What is the best/easiest way to avoid getting sick?

3. Viruses Tiny particles containing DNA and RNA
Requires a host cell to survive
Have SOME (not ALL) characteristics of life!

4. Virus Structure All viruses have the same basic structure!
Inner core made up of nucleic acid.
Capsid  protein coat surrounding the inner core

5. Examples
Bacteriophage – virus that infect bacteria
Influenza, HIV

6. How Do Viruses Work? https://www.youtube.com/watch?v=Rpj0emEGShQ
Must have a host cell (can be any living cell, but viruses are specific!)
Attach  Capsid of a virus binds to receptors on surface of host cell
Inject  Injects its DNA/RNA into host
Assemble  host cell begins making viruses (it’s been HIJACKED!)
Repeat  host cell eventually bursts, releasing hundreds of newly formed viruses to infect surrounding cells

7. Lytic Cycle Virus enters host cell. Virus destroys cell’s DNA.
“Tricks”/”reprograms” cell to make virus parts.
New viruses are built/assembled inside cell.
Cell bursts (dies) releasing viruses!

9. Lysogenic Cycle (longer name, longer cycle)
Virus enters host cell.
Virus inserts its genetic information into the host’s DNA molecule.
At this point, it doesn’t interfere with the cell’s function, it is copied along with the cell’s DNA, and passed on to future cells.
Virus DNA can be activated and enter the lytic cycle at any time. (reproducing viruses and killing the cell.)

11. Viruses can cause disease too!
Common Cold
Hepatitis A, B, C
Herpes
Mononucleosis
Warts
Chickenpox
Flu
AIDS
Ebola

12. There are vaccines to protect us against some viruses!
The good news is…
There are vaccines to protect us against some viruses!

13. Viruses in the News… Zika Virus

14. Viruses in the News… Ebola https://www.youtube.com/watch?v=XCrOde-JYs0

15. Review!

16. Viroids & Prions Infectious agents! (non-living)
Viroids  short strands of circular RNA with no protein coat, typically affect plants
Prions  small, misfolded proteins, affect animals (one causes Mad Cow disease)

17. Bacteria Prokaryotic Unicellular Contain DNA and ribosomes
Prokaryotic
Unicellular
Contain DNA and ribosomes
Have ALL the characteristics of living things!
Reproduce through binary fission

18. Evolution Bacteria reproduce very quickly (via binary fission).
This means evolution can occur very quickly!
Bacteria can exchange genetic info in 3 ways:

19. Basic Structure of Bacteria
Cell wall – for protection, support, rigidity, made of peptidoglycan (sugars and amino acids)
Cell membrane
Cytoplasm
Ribosome
Plasmids – circular DNA, used to exchange DNA between bacteria
Capsule – covers outside cell wall
May have pili, flagella, etc.

20. Bacteria have 3 distinct shapes:
Spherical (cocci)
Rod-shaped (bacilli)
Spiral (spirilla)

21. Gram Staining of Bacteria
Process used to separate bacteria into 2 large groups, based on chemical and physical properties of their cell wall, for medical diagnosis purposes.
Gram positive bacteria: Those bacteria when they are stained in gram stain results in purple color  (more peptidoglycan in cell wall)
Gram negative bacteria: Those bacteria when they are stained in gram stain results in pink color.
MOST pathogenic bacteria are gram negative!

23. Uses of Bacteria
Food (buttermilk, yogurt, cheese, sauerkraut, pickles, olives, etc…)
Decompose organic matter (recycle nutrients from dead organisms; break down sewage into simple compounds)
Nitrogen fixation (chemically changes nitrogen gas into a usable form for plants)
Human health (bacteria on skin help prevent infection, bacteria in gut aid digestion)
Biotechnology (used to make antibiotics, insulin, human growth hormone, vitamins)

24. Pathogenic Bacteria Bacteria typically cause disease by:
Releasing toxins  bacteria release a toxin (poison) into the bloodstream and it travels throughout the body

25. …BUT they cause a variety of diseases!
Pathogenic Bacteria… Less than 1% of bacteria cause disease in humans, animals, & plants!
…BUT they cause a variety of diseases!
Food poisoning
Tuberculosis
Cholera
Syphilis
Ulcers
Strep Throat