1. Bacteria & Viruses

2. What do you already know?
What are the differences between viruses and bacteria?
Are all bacteria harmful?
When you get a cold, should you take an antibiotic to help you get better?
What’s the best and easiest thing to do to avoid getting sick?

3. Bacteria
Bacteriology is the study of bacteria
Bacteria are prokaryotic, unicellular organisms containing DNA and ribosomes.
Bacteria have ALL the characteristics of living things.
Bacteria have the greatest percentage of the biomass on Earth!

4. Basic structure of bacteria:
Bacterial Structure
Basic structure of bacteria:
Cell
wall
Cell
membrane
Ribosome
Peptidoglycan*
Flagellum
DNA
Pili

5. Bacteria have three distinct shapes:
Bacterial Structure
Bacteria have three distinct shapes:
spherical
(cocci)
rod-shaped
(bacilli)
spiral
(spirilla)

6. Bacteria have a variety of important uses:
Help make interesting food (buttermilk, yogurt, cheese, sauerkraut, pickles, and olives, etc…)
Decompose organic matter (recycle nutrients from dead organisms; break down sewage into simpler compounds)
Nitrogen fixation (chemically changes nitrogen gas, N2, into ammonia, NH3, so plants can make amino acids)
Human health (bacteria on skin help prevent infection & bacteria in gut helps digest food & make vitamins)
Biotechnology (used to make antibiotics, insulin, human growth hormone, vitamins, and other drugs)

7. VIDEO CLIP: Understanding Bacteria
Less than one percent of bacteria cause disease in humans, animals, and plants.
Bacteria can cause a variety of diseases:
Food Poisoning – Scarlet Fever
Tuberculosis – Whooping Cough
Cholera – Bacterial Meningitis
Syphilis – Pneumonia
Ulcers – Leprosy
Strep Throat – Tetanus
VIDEO CLIP: Understanding Bacteria

8. Amoeba Sisters Presents

9. *So are viruses living or non-living?*
Virology is the study of viruses
Viruses are “biological entities” containing either DNA or RNA that require another cell to survive.
Viruses have some, but not all, of the characteristics of life.
*So are viruses living or non-living?*
Viruses seem to exist only to make more viruses!

10. (or RNA)

11. Nucleic acid core (DNA or RNA)
Viral Structure
All viruses have the same basic structure:
Nucleic acid core (DNA or RNA)
Capsid (Protein coat)

13. Without a host cell, viruses cannot function (i.e.-are harmless!)
How Do Viruses Work?
In order to replicate and make copies of itself, viruses need a host cell. Any living cell can become a host cell (human, animal, plant, and even bacterial cells!)
Without a host cell, viruses cannot function (i.e.-are harmless!)
Although any cell can theoretically become a host cell, specific viruses will only infect specific cells
(EX: HIV will only infect human T cells, a part of your immune system)

14. How Do Viruses Work?
Attach: The capsid of the virus binds to receptor proteins on the surface of a host cell, tricking the host cell into thinking it’s not a foreign invader.
Inject: The virus then injects its genetic material (DNA or RNA) into the host cell.
Assemble: The viral genes are expressed, turning the host cell into a virus-making factory.
Repeat: The host cell eventually bursts, releasing the hundreds of newly formed viruses to infect surrounding cells!
VIDEO CLIP:
How Viruses Work

15. Lytic Infection -a virus enters a bacteria cell (host) -makes copes of itself -causes host cell to burst (lyse)

16. Lysogenic infection -host cell is not immediately taken over -viral nucleic acid is inserted in to the host cells’ DNA and copied along with the host cell’s DNA without damaging the host -Viral DNA multiplies as the host cell multiplies: so each new daughter cell reproduced will have a copy of the virus -Bacteriophage DNA that becomes embedded in a bacterial hosts’ DNA = prophage -Prophage may remain a part of the DNA of the host cell for generations -environmental influences like radiation, heat, and chemicals trigger the prophage to become active -lysogenic infection actively becomes a lytic infection -Lytic and Lysogenic process happens similarly in eukaryotic cells

18. RETROVIRUSES
Retrovirus infection: RNA virus that copies its genetic information from RNA to DNA -infects cell -makes a DNA copy of its own RNA -inserts into the DNA of the host cell similar to lysogenic infections of bacteria Example: HIV, common cold

19. Viruses
Viruses can cause disease in humans, animals, plants, and even bacteria!
Viruses can cause a variety of diseases:
Common cold – Polio
Hepatitis A, B & C – Influenza
Herpes – Mumps
Mononucleosis – Measles
Warts – Viral Meningitis
Chickenpox – AIDS
VIDEO CLIP:
Viral Disease

20. Protection
There are a few big ways to protect yourself against pathogens (disease causing agents)
Antibiotics (drugs to kill bacteria)
Antivirals (drugs to treat viruses)
Vaccination (using your body’s own immune system to preemptively guard against attack)

21. Antibiotics
Antibiotics can only be used to treat bacterial infections!
Target specific structures on bacteria to kill them.
First made from a fungus (penicillin), now most are made artificially.
Unfortunately, antibiotic resistance (where the antibiotic doesn’t kill the target bacteria anymore) is becoming a major problem.

22. Antivirals
Antivirals can only be used to treat certain viral infections!
Does not “kill” or disarm the virus permanently; only shortens symptoms by 1-2 days.
Usually only prescribed to patients with life threatening symptoms or those that have a greater chance of developing complications (because of their age or they have a high-risk medical condition).
Just like antibiotics, there is evidence of antiviral resistance too!

23. Vaccination
Vaccines can only be used to prevent infections (both viral and bacterial) from leading to disease.
“Trick” your immune system to make antibodies that destroy foreign “bodies” or particles (such as bacteria and viruses). Your body remembers how to make these antibodies when the real thing invades.
Made from a weakened virus, inactivated virus, or by using only part of the virus/bacteria itself.
VIDEO CLIP:
Vaccination

25. To Review....
What are the differences between viruses and bacteria?
Are all bacteria harmful? Explain.
When you get a cold, should you take an antibiotic to help you get better? Why?
What’s the best and easiest thing to do to avoid getting sick?

26. More Amoeba Sisters

27. Bacteria
Virus
Both