1. Viruses

2. What are Viruses?
Virus—a nonliving particle made of a nucleic acid (DNA or RNA) and a protein coat called a capsid.
Virology—study of viruses

3. Living or Nonliving? Reasons viruses are NOT living organisms:
Cannot grow, develop, or move (they are carried)
Cannot reproduce on its own

4. Viral Structure and Attachment
Nucleic Acid
Capsid
A Bacteriophage ( a virus that only infects bacteria)

5. Viral Structure and Attachment
In general, viruses are species specific and some are cell type specific.
Species specific viruses can help control the spread of a viral disease (Ex. Smallpox) because they are more readily contained than viruses that can affect both animals and humans (Ex. Influenza aka “The Flu”)
The recognition and attachment process is like two pieces of a puzzle fitting together.

6. Viral Replication Cycles
1. Lytic Cycle: when a virus uses the host cell’s energy to make new viruses and kills the cell in the process.
2. Lysogenic Cycle: when the virus’s nucleic acid is incorporated into the host cell’s chromosomes.

7. Viral Replication Cycles
Lytic viruses cause disease immediately
Lysogenic viruses take longer to actively cause infection and they often reoccur:
Ex. herpes simplex I (causes cold sores in the mouth) and herpes simplex II (causes genital herpes).

8. FYI: Lytic Cycle
Chromosome
Virus
Host cell
2. Virus injects its chromosome into the host cell *INCORPORATION*
1. Virus attaches to a host cell
*ATTACHMENT*
3. The virus chromosome uses the host cell to make more viruses *REPLICATION*
4. New viruses bust out of the host cell, killing the host cell *INFECTION*

9. FYI: Lysogenic Cycle
Chromosome
Virus
Host cell
2. Virus injects its chromosome into the host cell
1. Virus attaches to a host cell
3. The virus chromosome is placed into the host cell’s chromosome.
Provirus: viral genetic material that is placed into the host cell’s chromosome
4. When the cell reproduces, the provirus is copied as part of the chromosome

10. Releasing Viral Particles
Exocytosis: the virus is packaged in small pieces of plasma membrane that fuse with the host cell’s plasma membrane, releasing viruses
Sugar
Host Cell
Step 3
Step 1
Step 2

11. HIV
Retroviruses are the most complex RNA viruses and they only involve RNA.
Reverse transcriptase: an enzyme that makes DNA from the virus’s RNA (remember a virus is incorporated into the host cell’s DNA).
HIV is a virus that infects white blood cell.

12. HIV
People may be infected, but show no signs of the disease because the host cell still functions normally.
Spread by direct contact
Unprotected sex, blood transfusions, sharing needles for drugs
**Most people with an HIV infection will eventually get AIDS because over time, more WBC’s become infected and die.

13. Other Infectious Agents
Viroid—smallest known particle that can cause infections
circular, single strands of RNA
no capsid (protein coat)

14. Other Infectious Agents
Prions—proteins that do not have any nucleic acids, but instead cause other proteins to fold incorrectly.
responsible for many animal diseases like mad cow disease and the human equivalent Creutzfeldt-Jakob disease.
ex. Kuru—occurred in many tribal places

15. Other Viral Diseases
Tobacco mosaic virus: first virus to be discovered (1930).
common cold
Hepatitis family (B & C are the most common in the US and can be sexually transmitted)

16. Other Viral Diseases
Ebola: % mortality; Biosafety Level (BSL) 4 –there are only a few found in the major countries of the world

17. Prevention and Treatment
1. Interferons- proteins in the immune system that inhibit viral replication within other cells of the body
2. Vaccines- contain live or dead viruses and they trick the body into thinking it’s already infected.
3. Antiviral drugs- they are made to destroy viruses or to prevent viral replication.

18. Treatment
Antibiotics Generally WILL NOT WORK ON Viruses!!!

19. Vaccination with Cowpox
A cartoon satirizes British physician Edward Jenner, who is shown injecting patients with cowpox virus, resulting in their transformation into cows. Jenner lived from 1749 to His discovery that cowpox was an effective vaccine against smallpox was initially greeted with skepticism, but soon accepted. The procedure dramatically reduced the incidence of smallpox, once a major cause of death in the 18th century.
Microsoft ® Encarta ® Encyclopedia © Microsoft Corporation. All rights reserved.

20. Kingdom Archaebacteria and Kingdom Eubacteria

21. Prokaryote vs. Eukaryote
Prokaryotic Cells
Eukaryotic Cells
No nucleus
Has a nucleus
Unicellular
Unicellular or Multicellular
No membrane bound organelles
Membrane bound organelles
Kingdoms Archaebacteria and Eubacteria
Kingdoms Protista, Fungi, Plantae, and Animalia

22. Prokaryotes Prokaryotes are classified into 2 different kingdoms:
Archaebacteria: live in extreme environments
Eubacteria: common bacteria that live almost everywhere

23. Kingdom Archaebacteria
Live in extreme habitats that are usually very low in oxygen
Types of Archaebacteria
1. Methanogens—produce methane (a gas)
–Live in marshes, lake sediment, digestive tracts, sewage treatment plants
–Oxygen is a poison– need anaerobic conditions

24. Kingdom Archaebacteria
2. Halophiles– like salty environments
–Great Salt Lake, Dead Sea
–use salt to make ATP (energy)
3. Thermophiles– live in hot, acidic sulfur springs and deep ocean vents

25. Kingdom Eubacteria Live almost everywhere Some are heterotrophs:
Use organic molecules as food
Some are parasitic
Saphrophytes—organisms that feed on dead organisms or organic waste

26. Kingdom Eubacteria Some are photosynthetic autotrophs:
use sunlight to carry out photosynthesis and make their own food
Some are chemosynthetic autotrophs:
Carry out chemosynthesis:
process of breaking down and releasing energy of inorganic compounds containing sulfur and nitrogen

27. The Structure of Bacteria
DNA (chromosome)
capsule
flagella
pili

28. The Structure of Bacteria
Do not have a nucleus, but do have a cell wall, cell membrane, cytoplasm and ribosomes
Some have a capsule: shell covering the cell wall that helps to protect the cell
Some have pili: short hairlike structures on the surface of the cell that helps to hold onto host cells
Many have flagella: whiplike structure on the surface of the cell that helps in movement

29. Identifying Bacteria 1. Gram staining
stains give bacteria color under a microscope
Gram staining is based upon the type of cell wall bacteria have:
Gram positive bacteria stain purple
Gram negative bacteria stain pink
Importance: certain antibiotics only work on Gram positive bacteria while others only work on Gram negative bacteria

30. Identifying Bacteria 2. By shape: 1. Rod (Bacilli) 2. Sphere (Cocci)
3. Spiral (Spiralla)
Chains begin with the prefix strepto-
Clusters begin with the prefix staphlo-

31. Streptococci pyogenes: Necrotizing Fasciitis
Facts:
- If they get under the skin, they infect soft tissues and they are known as the flesh eating bacteria.
Approx cases a year in the US

32. Vibrio cholerae: Cholera (a bacilli)
Facts:
-One of the most rapidly fatal diseases known
Found in contaminated water…how would it have gotten there???
Last outbreak in the U.S. was back in 1911, but it’s still a problem in less developed countries

33. Treponema pallidium: Syphillis (a spiralla)
Facts:
- A curable STD
- If untreated, can cause serious damage to the body and deterioration in the brain, leading to madness or even death.

34. Bacterial Reproduction
Can’t reproduce by meiosis or mitosis because they don’t have a nucleus
So, how do they do it???
1. Binary fission: asexual reproduction because a bacterial cell copies itself
2. Conjugation: sexual reproduction because a bacterial cell connects to another bacterial cell through the pilus (plural, pili) and then transfers all or part of its DNA to the second bacterial cell

35. Factors affecting growth
Growing conditions must be right
Obligate anaerobes– bacteria that cannot survive in presence of oxygen
Ex: Tetanus (Lock jaw): puncture wound deep into skin provides oxygen-free environment for this bacteria
Facultative anaerobes– can live with or without oxygen
Ex: E. coli in intestines
Obligate aerobes– bacteria that can’t survive without oxygen.
Ex: bacteria that causes TB

36. Survival Under unfavorable conditions, some bacteria form endospores
Endospore—structure that contains bacterium’s DNA and cytoplasm. Covered by tough outer protective coating.
Resting stage—no reproduction

37. Survival When conditions improve, endospore will germinate/reproduce
Example: When canning foods, we must sterilize jars and acidify food  prevents food poisoning with botulism
Example: Tetanus forms endospores. When spore enters body through wound, will germinate and release toxins that lead to neurological problems.

38. Helpful Bacteria Uses: Sewage treatment plants—break down wastes
Food processing—bacteria create buttermilk, sour cream, yogurt, cheese, sauerkraut, some pickles
Chemicals—insecticides, clean up oil spills, genetic engineering (making insulin)
Nitrogen fixation—can take nitrogen gas and put it into useful compounds