1. Viruses & Bacteria
Chapter 19

2. Studying Viruses & Prokaryotes
Virus is an infectious particle made only of a strand of DNA or RNA that is surrounded by a protein coat
Bacteria one-celled microorganisms that can also cause infection
Pathogen any living organism or particle that can cause an infectious disease

3. Characteristics of all living things
Ability to reproduce
Use nutrients and energy
Grow and develop
Respond to their environment
Have genetic material

4. Soo what are viruses? Viruses can respond to their environment
They can obtain energy
BUT THEY CANNOT REPRODUCE ON THEIR OWN
Viruses are parasites that need a host in order to live, grow, and reproduce
Viruses are much smaller than cells
Viruses are not given a place in Linnaean classification

5. Virus INFO Viroid infectious particles that cause disease in PLANTS
They are made of single-stranded RNA without a protein coat
They are passed through seeds or pollen
Can cause havoc to agriculture by stunting the growth of plants

8. Virus INFO
Prion an infectious particle made only of proteins that can cause other proteins to fold incorrectly
They are very unusual because they have no genetic material
Diseases caused by prions
Mad cow disease
Bovine spongiform encephalopathy
Creutzfeld-Jakob disease

9. Videos https://www.youtube.com/watch?v=aP-ShyyHiIc

10. Viruses Dmitri Ivanovsky made the discovery of the virus
He studied tobacco mosaic disease name for the scar tissue it leaves on the leaves of tobacco plants
He thought it was caused by a bacterium
Ivanovksy passed extracts of diseased tobacco leaves through filter pores small enough to strain out bacteria and found that the extracts could still pass on the disease
How could this be? New bacteria? Unknown organism?

11. Viruses In 1898 Martinus Beijerinck built upon Ivanovsky’s work
He proposed that tiny particles within the extracts caused the infection
Name them virus (meaning poison in latin)

12. Structure of a Virus A single viral particle can be termed a virion
Each virion has a protein shell called a capsid
Some are surrounded by a lipid envelope
Spiky structures can protrude from the envelope to protect the virion
Some viruses attach to a cell with the spikes

13. Reproduce
Viruses can only reproduce after they have infected host cells
They can move from one host cell to the next because they have no cell structure maintaining them or constricting their spread
All it needs to reproduce is its genes

14. Structure of a Virus Viruses can have several shapes and sizes
Each type of virus can infect only certain hosts
A virus identifies its host by fitting its surface proteins to receptor molecules on the surface of the host cell (fits like a lock and key)
Some viruses can infect several species some can only infect single species

15. Structure of a Virus

16. Viruses that infect Bacteria
Bacteriophages viruses that infect bacteria
E. coli is an example of a bacteriophage that infects our intestines and makes us very ill

17. Viruses that infect Eukaryotes
These viruses differ from bacteriophages because of their methods of entering the host cell
Many enter by endocytosis
Endocytosis is the process of forming vesicles around the virus and attaching to the plasma membrane
Vesicle is formed by the envelope on the virus
They then enter into the cytoplasm and target the nucleus

18. Infection Types Lytic Infection Lysogenic infection
The cell bursts releasing the new viral offspring into the host’s system
Combines its DNA into the hosts DNA

21. First Defenses
Skin viruses can only pass through the skin by entering through a cut or scrape, or any other opening in the body
Mouth, nose, genital areas, eyes, and ears
Receptors on cells lock out the virus
Proteins on the surface of the viral capsid trick the receptors into letting it in

22. Viral Infections Common cold:
200 different viruses can cause the common cold
They can mutate and change before you give it to the next person
Usually last a week and there is no medication to help fight the virus

23. Viral Infections Influenza: Can cause an epidemic
Flu virus
Spreads very quickly
Can cause an epidemic
Epidemic a rapid outbreak of an injection that affects many people
20% of the US population get influenza each year

24. Influenza 3 types of Influenza’s can infect humans
Some viruses can mutate and cause the flu to pass between different species
Vaccine substance that stimulates the body’s own immune respone against invasion by microbes

25. HIV Human Immunodeficiency virus
HIV is a retrovirus is a virus that contains RNA and uses an enzyme called reverse transcriptase to make a DNA copy
This DNA can remain dormant for years as a provirus, causing no symptoms to its human host
DNA usually spreads via the lytic cycle and this causes the virus to kill our white blood cells which ultimately causes AIDS
Many medications and antiviral drugs developed to fight HIV

26. Vaccines
Vaccines are made from the same pathogen that it is supposed to protect against
Vaccines consist of weakened versions of the virus that will cause the body to produce a response
When the body encounters the virus the body can naturally fight it off because of the vaccine

27. Prokaryotes Archaea and bacteria
These are the most wide spread and abundant organisms on earth
Thought to be 1030 types of prokaryotes on earth
Many still unknown
One gram of soil may contain up to 5 billion bacterial cells with 10,000 different types of bacteria

28. Prokaryotes
Obligate Anaerobes prokaryotes that cannot live in the presence of oxygen
Obligate Aerobes prokaryotes that need oxygen in their environment
Facultative Aerobes can survive in the presence or absence of oxygen

29. Prokaryotic Domains
All prokaryotes are single celled, have cell walls and plasma membrane, no organelles, circular DNA in the cytoplasm, many move using flagella
Plasmid a small piece of genetic material that can replicate separately from the main chromosome
Flagellum whip like structure outside of a cell that is used for movement

30. Prokaryotic Cell

31. Bacteria shapes Archaea shapes can vary immensely
Bacteria tend to have 3 shapes
Rod shaped bacilli
Spiral shaped spiralla
Spherical shaped cocci

32. Bacteria Shape

33. Prokaryotes Archaea Bacteria Live in harsh conditions
Cell wall is not made of peptidoglycan
Rarely causes disease in humans
Cell wall differences cause medicine to be ineffective
Cell walls made of peptidoglycan
Lives in moderate conditions
Medication kills bacteria cells

34. Gene Exchange
Prokaryotes reproduce via binary fission (2 exact copies made with full amount of DNA)
Prokaryotes can exchange genetic material to increase genetic diversity
Conjugation exchange parts of their chromosomes through a hollow bridge of pili formed to connect two or more cells
Prokaryotes can survive unfavorable harsh conditions with the help of endospores
Endospores cell with a thick protective wall

36. Endospore
Endospores form by coping their chromosomes and produce a wall around the copy
The thick wall can protect DNA from drying out, temp. changes, and disinfectants
Can last for centuries

37. Endospore

38. Nutrients Prokaryotes provide nutrients to humans and animals
In humans we have bacteria in our intestines that assist us digest food.
This is a mutualism relationship
Many foods we enjoy are fermented by bacteria
Yogurt
Cheese
Vinegar
Pickles
Soy sauce

39. Prokaryotes in Ecosystems
Prokaryotic cells in our ecosystem can help break down carbon, nitrogen, and hydrogen
Cyanobacteria release oxygen into the atmosphere
Legumes are nitrogen-fixing bacteria that are free-living
Soybeans, beans, alfalfa, clover
This is the purpose of crop rotation

40. Ecosystem Continued
Some prokaryotes help break down pollutants Bioremediation
Used to clean up oil spills (BP oil spill they fertilized beach to grow bacteria)
Bacteria can break down basically any human waste which is very useful
One important product they cannot break up is plastic (DO NOT LITER)

41. Bacteria causing diseases
Some bacteria can cause disease in plants and animals by disrupting the host organism’s homeostasis
Can cause disease in 2 basic ways:
Invade tissue and attack cells
Make poisons
Toxin a poison that is released by an organism

42. Tuberculosis Caused by the bacteria Mycobacterium tuberculosis
Multiply in the lungs killing the white blood cells that respond to invasion
They body reacts by swelling and this can damage the lungs

43. Read pg. 575-575 Staph infections
Discuss what they are and how they are spread

44. Antibiotics
Antibiotics kill off harmful bacteria that make someone sick
Prime example Streptococcus or the common term “strep throat”
Strep throat is a bacteria that can be killed with a antibiotic
Medicine can be made naturally by bacteria or fungi
It is important not to over medicate because this can kill good bacteria that helps fight diseases and other purposes

45. Resistance
Drug resistance is the product of natural selection, as individuals who are more resistant are more likely to survive and reproduce
Some bacteria are killed by the same antibiotic
This allows for bacteria to become resistant by forming plasmids
Plasmid small portion of DNA that holds certain genes (resistance)

46. Reasons for resistance
Overuse
If you use a antibiotic when you are not sick with a bacteria it kills good cells and makes other resistant
Underuse
If you do not use the medication for its prescribed length of time it allows bacteria cells to adjust and become resistance
Misuse
We eat livestock that are medicated heavily to grow faster, and this can cause our bacteria cells to become resistant