Viroids, Prions, Viruses, and Bacteria Chapter 20

Viroids, Prions, Viruses, and Viroids, Prions, Viruses, and BacteriaBacteria

Chapter 20Chapter 20

Thinking Question #1 (Partner Activity)

A. What is the difference between a bacteria and a virus?

B. Are both considered cells? Why or why not?

C. Of the following diseases which are caused by viruses or bacteria?

-Measles -Chicken pox

- Aids, -Botulism

-Tuberculosis -Bubonic Plague

-Syphilis -Polio

-Flu -Mumps

- Lyme disease - Strep throat

- Common Cold

D. Can antibiotics cure all of these diseases, why or why not?

VirusesViruses

• Viruses are extremely small, non-living, disease-causing Viruses are extremely small, non-living, disease-causing pathogens that have the ability to infect any organism pathogens that have the ability to infect any organism including bacteria.including bacteria.

• Viruses are composed of a protein coat (capsid) with Viruses are composed of a protein coat (capsid) with either viral DNA or viral RNA.either viral DNA or viral RNA.

• Viruses may only replicate in a living organism. They do Viruses may only replicate in a living organism. They do not have the ability to reproduce on or in a non-living not have the ability to reproduce on or in a non-living surface. surface.

Flu virus - http://science.nationalgeographic.com/science/photos/influenza/flu-virus.html

Thinking Questions #2

• Thinking Question #2: What is a pathogen?

Viruses

• Viruses are so small, that they were not discovered until the end of the 19th century when they were trying to find the pathogen that caused tobacco mosaic disease (TMV).

• Once discovered, it was called a virus, which is Latin for “poison.”

• In 1935, Wendell Stanley finally purified and crystallized the TMV virus.

What Are Viruses?

• If you recall, Rosalind Franklin, the same one whose photo 51 of crystallized DNA was “taken” by Watson & Crick, pursued other research interests and began working on trying to figure out the anatomy of a virus.

• This is what she and others found.- 1.)The virus has a protein coat or capsid. 2.) A virus may contain either DNA or RNA, but not

both. 3.) Some viruses have an additional membrane or

envelope.

Structure of Influenza Virus

Viral Structures

Figure 1

An array of viruses. (a) The helical virus of rabies. (b) The segmented helical virus of influenza. (c) A bacteriophage with an icosahedral head and helical tail. (d) An enveloped icosahedral herpes simplex virus. (e) The unenveloped polio virus. (f) The icosahedral human immunodeficiency virus with spikes on its envelope.

Classification of Viruses

• Viruses can be classified according to the following characteristics.- 1.) Whether or not they contain DNA or RNA 2.) Their shape 3.) What they infect 4.) Their genetic make-up 5.) The type of disease that they may cause The group of viruses that infect bacteria are

called bacteriophages.

Bacteriophage

Thinking Question #2

• Thinking Question #3: How does a virus get into a cell?

Virus Movie

• Virus Animation

How Does A Virus Get Into A Host Cell

• Viruses “know” which organisms to infect because Viruses “know” which organisms to infect because they try to attach to specific receptor sites, which are they try to attach to specific receptor sites, which are usually proteins that are found on the cell usually proteins that are found on the cell membranes of an organism.membranes of an organism.

• Once the virus has recognized and attached to the Once the virus has recognized and attached to the specific organism’s cell membrane receptor site, the specific organism’s cell membrane receptor site, the virus gains entry by one of two waysvirus gains entry by one of two ways

1. Endocytosis1. Endocytosis2. Virus injects its DNA or RNA into the cell of 2. Virus injects its DNA or RNA into the cell of

the the organism. organism.

• http://www.courses.fas.harvard.edu/~biotext/animations/viralinfection.html

Virus Entry

Lytic vs. Lysogenic Cycle

• Once inside the cell, one of two things can happen. 1.) The virus can lay dormant (asleep) inside the cell

and not cause the organism to get sick. This is called the lysogenic cycle. Diseases that ‘keep showing up’ such as herpes could be considered lysogenic.

2.) The virus hijacks the cell’s normal cellular functions and tricks the cell into making more viruses. This will eventually kill the cell and cause more viruses to be released. This is called the lytic cycle. Diseases that begin and end over a short period of time such as a cold could be considered lytic.

Lysogenic Cycle

Animation

• Lysogenic Cycle Animation

• http://www.courses.fas.harvard.edu/~biotext/animations/lysogeny.html

Lytic Cycle

http://www.web-books.com/MoBio/Free/Ch1F1.htm

Lytic Cycle

• Lytic Cycle Animation

• http://www.courses.fas.harvard.edu/~biotext/animations/lyticcycle.html

Thinking Question #4

• Thinking Question #4: What do you think causes a virus that is in the lysogenic cycle to become lytic (Example: Someone that has not had a herpes outbreak for years suddenly has one)

Thinking Question #3

• Thinking Question #5: How do you get a virus? How are viruses spread?

Viral Transmission

• You cannot catch a viral disease from simply touching or sitting on a surface. The only ways that you can catch a viral disease is from direct contact, an injection, inhalation, or spreading infected body fluids into a cut, your mouth, your nose, or your eyes.

• Many recent studies have shown that by simply washing your hands prior to eating, rubbing your nose, or rubbing your eyes, you can exponentially reduce your chances of getting a viral infection.

http://www.foodlink.org.uk/factfile_c.asp?file=2&chapter=2http://www.bma.org.uk/ap.nsf/Content/viralrespiratorydisorders~spreadhttp://www.cnn.com/2007/HEALTH/10/31/flu.dos.donts/index.htmlhttp://www.sciencedaily.com/videos/2005/1212-fighting_cold_and_flu_germs.htm

http://www.southcoast.org/24/flu.htmlhttp://www.wcu.edu/4995.asphttp://www.health.gov.sk.ca/influenza-schools-parents

Some of the diseases which Some of the diseases which are caused by viruses:-are caused by viruses:-

• AIDSAIDS• The common coldThe common cold• EbolaEbola• Hepatitis A and BHepatitis A and B• Influenza or the fluInfluenza or the flu• MumpsMumps• PolioPolio• RabiesRabies• SmallpoxSmallpox

Lab Activity

• Pass It On

Virus Prevention

• Inactivated Vaccine: made of virus particles that have been killed and cannot replicate. The virus capsid proteins are still intact enough to be recognized by immune system and evoke a response

• Attenuated Vaccine: Vaccine which uses “live” but weakened/altered virus so it is less virulent. Preferred because these vaccines last longer

• Antiviral Drugs: drugs that interfere with viral nucleic acids and viral reproduction used to treat HIV, herpes, influenza

•

Thinking Question #6

• Are there other types of pathogens besides viruses and bacteria?

PrionsPrions

• Pathogens discovered in the 1980s and have since Pathogens discovered in the 1980s and have since been shown to be involved a variety of diseases, been shown to be involved a variety of diseases, such as Kuru, Mad Cow, and other brain illnesses.such as Kuru, Mad Cow, and other brain illnesses.

• Prions are proteins that “have gone bad.” They find Prions are proteins that “have gone bad.” They find their way into the brain and cause the proteins in the their way into the brain and cause the proteins in the brain to change shape.brain to change shape.

• These newly shaped proteins then create plaques or These newly shaped proteins then create plaques or hard parts in the brain. (The brain is not supposed to hard parts in the brain. (The brain is not supposed to have these plaques.).have these plaques.).

http://jackson.ifas.ufl.edu/bse.htm

http://www.ens-newswire.com/ens/jul2006/2006-07-10-03.asphttp://scienceblogs.com/retrospectacle/2007/02/basic_concepts_prions.phphttp://www.sciencemag.org/feature/data/prusiner/245.dtl

http://www.biologie.uni-duesseldorf.de/Institute/Physikalische_Biologie/Research/Topics/addinformation2http://www.cnspathology.com/

Fig 1: Histopathology shows spongiform changes in brain of A sporadic CJD, B new variant CJD, C Kuru and D BSE (pictures A-C Hans Kretzschmar, M 殤 chen, D Martin Groschup, Insel Riems)

Healthy Brain tissue - Note few ‘holes.’

• http://highered.mcgraw-hill.com/sites/dl/free/0072835125/126997/animation44.html

• http://www.youtube.com/watch?v=H2Ouxl_GNjA

ViroidsViroids

• These are newly discovered infectious agents These are newly discovered infectious agents that are single pieces of RNA that lack a capsidthat are single pieces of RNA that lack a capsid

• Several have been identified as plant pathogens Several have been identified as plant pathogens while only one so far has been identified as a while only one so far has been identified as a human pathogen (hepatitis delta).human pathogen (hepatitis delta).

http://www.biologie.uni-hamburg.de/bzf/mppg/agviroid.htmFig. 2: Symptoms of viroid diseases: A: potato spindle tuber on tomato, B: avocado sun blotch, C: chrysanthemum stunt, D chrysanthemum chlorotic mottle

http://www.virtualology.com/virtualmuseumofnaturalhistory/halloftaxonomy/viruses/viroids.org/

BacteriaBacteria

• The ancestors of these organisms are The ancestors of these organisms are considered to have been some of the first life considered to have been some of the first life forms on Earth given the fossil record.forms on Earth given the fossil record.

• Thinking Question #7: ReviewThinking Question #7: ReviewA. Are bacteria prokaryotic or eukaryotic, why?A. Are bacteria prokaryotic or eukaryotic, why?

http://www.ucmp.berkeley.edu/bacteria/cyanofr.html

Bacteria differ from eukaryotes in at least 7 ways.

• No organelles

• Cell size: (1u-5u)

• Unicellular

• Plasmids (single circular piece of DNA)

• Binary fission

• Flagella (single flagellum in bacterial cells) & Pilli (small outer growths enable bacteria to attach to cells or other surfaces

• Metabolic diversity

Bacterial Flagella & Pilli

• Bacteria have the ability to metabolize either Bacteria have the ability to metabolize either under the following conditions:under the following conditions: Anaerobic (no oxygen) Anaerobic (no oxygen) Aerobic (with oxygen) Aerobic (with oxygen)

• They may be: They may be: 1. Photosynthetic autotrophs1. Photosynthetic autotrophs2. Chemoautotrophs2. Chemoautotrophs3. Heterotrophs (decomposers)3. Heterotrophs (decomposers)

Metabolic Diversity

Photosynthetic bacteriaPhotosynthetic bacteria

• Photosynthetic Bacteria use energy Photosynthetic Bacteria use energy from sunlight to make foodfrom sunlight to make food

• Four types based on the photosynthetic Four types based on the photosynthetic pigments they containpigments they contain

1. Purple non-sulfur1. Purple non-sulfur

2. Cyanobacteria2. Cyanobacteria

3. Anaerobic purple sulfur3. Anaerobic purple sulfur

4.Anaerobic green sulfur4.Anaerobic green sulfur

Chemoautotrophic Bacteria

• Chemoautotrophic Bacteria: use inorganic molecules such as ammonia, hydrogen sulfide, and methane to make their own food.

• Live in soil produce chemicals such as nitrates and phosphates, which help fertilize plants.

• Most bacteria are heterotrophsMost bacteria are heterotrophs• Bacteria, along with fungi, are the Bacteria, along with fungi, are the

main decomposers for most main decomposers for most ecosystems.ecosystems.

• Anaerobic fermentation (bacteria Anaerobic fermentation (bacteria help produce fermented food like help produce fermented food like cheese, vinegar & sour dough breadcheese, vinegar & sour dough bread

• ..

Heterotrophic Bacteria

Yogurt

Fungi

Bacteria

Thinking Question #8

• Thinking Question #5: Where are bacteria found?

http://www.nsf.gov/news/special_reports/sfs/index.jsp?id=life&sid=ext

Bacteria Bacteria Everywhere

• Since they have adapted a variety of Since they have adapted a variety of different ways to obtain food, they can different ways to obtain food, they can be found almost anywhere on Earth.be found almost anywhere on Earth.

• Often warm moist environments

• 80-100 F 90% water

Thinking Question #9

• Thinking Question #9 : So why do bacteria make us feel so sick? What are they doing inside our bodies?

So Why Do Bacteria Make us Feel So Sick

• Some bacteria produce toxins. These chemicals are what cause us to have nausea, diarrhea, and/or vomiting when we are infected with bacteria.

• Food poisoning

So Why Do Bacteria Make us Feel So Sick

• Some can not only produce toxins, but they can also secrete enzymes which destroy our normal cell’s functions.

• A human’s normal inflammatory response, which includes a fever, a human’s immune system, vaccinations, and prescribed antibiotics may be effective means to control the bacterial infection.

Examples of infections caused Examples of infections caused by bacteria are:-by bacteria are:-

• AnthraxAnthrax• Bubonic plagueBubonic plague• CholeraCholera• Dental cavitiesDental cavities• Lyme diseaseLyme disease• TuberculosisTuberculosis• TyphusTyphus• AcneAcne• Food poisoningFood poisoning

Bacteria come in three shapes.Bacteria come in three shapes.

• Bacillus or Rod-Bacillus or Rod-shapedshaped

• Coccus or roundCoccus or round

• Spirillum or Spirillum or spiralspiral

http://universe-review.ca/F11-monocell.htm

Bacterial Forms

• Some bacteria aggregate in specific ways. Strepto- bacteria group

together into long filaments.

Staphylo- bacteria group together into clusters.

Diplo: two Tetrad: four

http://www.ncl.ac.uk/dental/oralbiol/oralenv/tutorials/streps.htmhttp://nbsp.sonoma.edu/resources/presentations/derekpres/05Microbe%20lecture/sld003.htm

Bacterial Killers

• Thinking Question # 10: So what kills bacterial cells other than antibiotics?

Bacterial Killers

• Ammonia: disrupts bacterial cell membrane

• Alcohol: breaks down proteins

• Chlorine: destroys chemical bonds in bacteria

• Iodine: stops proteins from working

• Penicillin: stops cell wall formation