Viruses

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Viruses

• Latin Poison slippery toxin

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Virus Video

• http//www.youtube.com/watch?vL8oHs7G_syIlistPL
  7A750281106CD067index22

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Size comparisons
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What are Viruses?

• Smaller and simpler than bacteria
• NOT made up of cells
• Lack most metabolic machinery, so must hijack a
  cell to reproduce
• Are little more than a combination of nucleic
  acid and protein genes in a protein coat
• Viruses are NOT considered living things

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Viral Structure

• 2 parts
• Capsid protein coat
• Accessory structures that aid in host infection
• Viral envelopes- cloak capsid derived from
  hosts membrane
• Glycoproteins act as anchoring spikes
• Tail act as hypodermic syringe
• Nucleic Acid
• Genome
• DNA or RNA

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Common Viruses

• Flu Virus
• HIV Retrovirus
• Herpes Simplex I
• Chicken pox virus (shingles)
• West Nile Virus most people infected never know
  they have it!

Flu Virus
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Figure 18.02x2 Phages
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H1N1 Invading Lung Cells
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ClassificationViral Genomes Classification

• 4 Types
• 1. Double Strand DNA
• 2. Single Strand DNA
• 3. Double Strand RNA
• 4. Single Strand RNA
• Classified DNA-like or RNA-like/Retrovirus
• Further naming is based on surface proteins
• H1N1 H proteins hemoggluttin, N
  neuraminidase

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Viral reproductive cycle (Infection) - Overview

• Virus uses hosts machinery to replicate viral
  genome
• Hosts machinery used to make capsid proteins
• Use transcription and translation.
• New viral genomes and capsids are assembled into
  new viruses

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What is a good analogy for viral infection?
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Lytic vs. Lysogenic Cycles

• Lytic cycle -virus takes over the host cell
  immediately and reproduces quickly
• Virulent infections quick!
• Infections you get over
• Ex. Cold virus, influenza
• Lysogenic cycle - virus hides in hosts DNA
  until optimal conditions for viral survival are
  present
• Lifetime Infections
• Ex. HIV, herpes

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Lytic Cycle
Lytic Cycle Virus infect and use hosts machinery
to replicate many genomes and proteins Lyses
host cell quickly after replication and assembly
of new viruses
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5 Steps of Lytic Cycle

• 1. Attachment lock and key
• 2. Penetration genome injection
• 3. Genome Replication and Synthesis - hijack
  host machinery
• 4. Assembly - hijack host energy
• 5. Lysis (Release) burst free

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Lytic Virus
Lytic Bacteriophage
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Lysogenic Cycle Instead of Lysing the cell
quickly, virus hides out in host Replicates and
divides with host cells creating many new
viruses Conditions right, virus enters Lytic
Cycle, breaking the host cell, leaving to infect
more
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8 steps of the Lysogenic Cycle

• Attachment
• Penetration
• Integration into the hosts DNA (provirus)
• Replication of cells (including virus DNA)
  through mitosis
• Trigger stress, chemicals
• Replication Synthesis of Virus
• Assembly
• Lysis

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Lysogenic Virus
Prophage infection
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Ex Lysogenic CycleHerpsevirus in Humans

• Herpesviruses genomes of double-stranded DNA
• Reproduce within the cell nucleus
• Hides in cell DNA replicated during mitosis
• Infections tend to recur throughout life in times
  of stress ? viruses will emerge from thousands of
  cells then

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Figure 18.5 The lysogenic and lytic reproductive
cycles of phage ?, a temperate phage
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RNA Viruses and Retroviruses

• These viruses have a HIGH MUTATION RATE
• There is no good PROOFREADING mechanism like
  there is when going from DNA to RNA
• These means there are many different STRAINS of
  RNA viruses and Retroviruses
• Makes VACCINES very difficult to develop

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The Red Queen Hypothesis

• Evolution runs around to stay in the same
  place
• Disease/Host HIV fastest evolving thing on
  planet!
• Lysogenic viruses ALWAYS under selective pressure
  mutations selected for
• In 10 years an HIV infection will be up to 60
  different in RNA bases than the original strain

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Emerging/Zoonotic Viruses

• Host range is specific lock key
• Sometimes virus can mutate be able to change
  hosts
• Evolution
• Zoonotic Virus from different animal host
• Usually severe immunity?
• Ex Ebola, Hendra, Swine Flu

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Why not antibiotics?

• Antibiotics target cellular properties
• Cell wall of bacteria
• Antibiotics target life processes
• DNA replication
• Protein Synthesis
• Nyquil? Robitussin? Tylenol Cold?
• Immune System
• Destroys viruses physically or rids body of them
  - antibodies
• Keeps lysogenic hidden in genome
• Antiviral medicines
• Prevent HOST cells from life processes
• DNA replication or Protein Synthesis
• Ex Abreva, AZT

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Differences Between Bacteria and Viruses

• Bacteria are classified as living
• Bacteria are prokaryotic cells
• No Nucleus
• Bacteria can perform metabolic functions
• Replication
• Protein Synthesis
• Use and obtain own energy in various ways
• Move on their own

Viruses are not affected by antibiotics
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Vaccines the war against the virus

• Prevention
• Injecting WEAKENED or HEAT KILLED virus
  particles to cause your immune system to
  recognize the virus quickly
• Immune cells can recognize SHAPE of capsid or
  DNA/RNA markers
• Create antibodies (Memory cells B T cells)
• When in contact with the real virus, your IMMUNE
  SYSTEM should recognize the virus and come to the
  rescue

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Vaccine contributors

• Edward Jenner did early, important work using
  cowpox and smallpox viruses. He used cowpox to
  stimulate an immune response to the very similar
  smallpox virus
• Jenner tried out an early small pox vaccine using
  his SON in 1796

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Vaccine contributors

• Jonas Salk killed the polio virus but kept
  enough of it intact (protein capsid) so that they
  body could recognize the actual virus following
  exposure to the killed form.
• Albert Sabin felt that a weakened, live form
  would be more effective (mutated DNA) It is now
  the vaccine of choice, in part because it is
  actually cheaper and easier to make. The Sabin
  vaccine can cause polio in persons with a
  compromised immune system.

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Is this correct?!?!

• Kills 99.99 of germs

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Terms to know

• Temperate when the virus is dormant or inactive
• Virulent when a virus is active
• Pathogenic disease causing
• Epidemic
• Pandemic

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Viruses Going Further

• Oncogenic Viruses Lysogenic viruses that can
  lead to cancers insertion of viral genome
  mutates host genome ? Cancer
• HPV, Rouse Sarcoma
• Why we have the Guardasil Vaccine
• Prions Infectious protein particles that can
  change the shape (conformation) of normal
  proteins in the body
• Mad Cow Disease, Crutzfield-Jacob disease

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You be the Virologist!

• Now that weve lectured on viruses.
• Use your notes to answer the questions on a
  separate sheet.

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Understanding Viruses Video Questions

• Answer the questions during the film.

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Computer Lab Time

• Lets investigate some modern virus information!
• Choose 4/6 Sections (A F) to complete using the
  links provided on the sheet.

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The Amazing World of Bacteria
Bacteria on the point of a pin!!! Electron
Microscope 1500 x
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https//www.youtube.com/watch?vvAR47-g6tlAlistP
L3EED4C1D684D3ADFindex36
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Differences Between Bacteria and Viruses

• Bacteria
• Living
• Prokaryotes
• DNA
• Metabolic functions replication, protein
  synthesis, use and obtain own energy
• Move
• Reproduce
• Classified

• Virus
• Non-Living
• Cannot perform metabolic functions
• Some - no DNA
• Cannot move
• Cannot reproduce without a host
• Not classified

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Differences between Prokaryotes and Eukaryotes

• Prokaryotes
• No nucleus or membrane-bound organelles
• Unicellular only
• Eukaryotes are not AS affected by most
  antibiotics
• difference in cell wall
• metabolism
• Prokaryotes - extreme environments
• most eukaryotes cant tolerate
• Fun Fact there are more prokaryotes in a hand
  full of dirt (or cup full of sea water) than
  humans that have ever lived!!!

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2 Kingdoms of Bacteria

• Eubacteria
• Peptidoglycan in cell wall
• Affected by antibiotics
• Archaebacteria Ancient Bacteria
• Extreme Environments
• no peptidoglycan in cell wall
• not affected by antibiotics
• 3 Domain system - early divergence of 2 bacteria
  types
• Archaea and Bacteria
• We will focus on Bacteria (Eubacteria)

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Typical Prokaryotic Structure
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Movement

• Flagella help propel the cell
• On outside of cell wall
• Scattered all over surface or concentrated at the
  ends
• Cilia hair-like projections outside cell
• Slime oozes from cell
• helps bacteria glide along

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Flagella
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Cell Wall

• 2 different types in Eubacteria
• Peptidoglycan on outside layer
• Lipid carbohydrate layer over peptidoglycan layer
• Antibiotics target mainly peptidoglycan in cell
  wall
• To determine cell wall structure, use Gram Stain
  
• Gram () means peptidoglycan in outer wall -
  purple
• Gram (-) means outer layer of lipid/carb covers
  peptidoglycan layer- pink/red
• Antibiotics mainly kill Gram () bacteria

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Mix of Gram() and (-) Bacteria
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Endospore Bacterial Protection Phase

• If growth conditions are not suitable for
  bacteria
• It grows a thick wall of keratin protein around
  cell wall
• Protects
• Can remain dormant indefinitely
• Can grow once conditions return to favorable
• Why we must autoclave

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Naming bacteria shape and colony type

• Unicellular
• may aggregate in groups of two or more
• True colonies permanent groups of identical
  cells chains (strepto)
• clusters (staphalo)
• Differ in shape 3 most common
• spherical (coccus or cocci)
• rod-like (bacillus or bacilli)
• helical (spirillum or spirilla, spirochetes)
• Diameter ranges between 1-5 um largest is .75 mm
  in diameter

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Draw these shapes in your notes and know their
names!!!
Cocci
Bacillus
Spirillum
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Modes of Nutrition Very Diverse

• Nutrition of prokaryotes how org obtains energy
  and a carbon source to build org molecules
• 4 categories
• 1. photoautotrophs use light to make food
• 2. chemoautotrophs need CO2 as carbon source,
  and get chemical energy from inorganic substances
• 3. photoheterotrophs use light to make
  energy, but need a carbon source to start with
• 4. chemoheterotrophs must eat other
  organisms to get food in chemical form
• most bacteria are this type
• Saprobes decomposing bacteria
• Parasites infectious bacteria

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Reproduction Binary Fission

• Asexual Reproduction - No recombination of
  genetic material!
• Bacterial cell just splits in half and have two
  cells from the original
• Conjugation bacteria can swap plasmids (2nd
  genome)
• Primitive sexual reproduction?

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Prokaryotes are not all bad

• Many do cause disease, but others are symbiotic
  (E. coli in intestines), help with cycling
  nutrients (decomposers and carbon cycle)
• Many are important in food processing (yogurt,
  cheese, etc)
• Are about 5,000 species known, could be as many
  as 4 million

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Ecological Impact of Prokaryotes

• Recycling of nutrients (decomposers)
• Symbiotic relationships
• Cause many Diseases
• opportunistic
• Bioremediation use or orgs to remove pollutants
• Ex. Sewage treatment plants anaerobic prok
• Ex. Decompose petroleum compounds at oil spills
  -- pseudomonads
• Act as metabolic factories for human use
• -produce acetone, butanol
• -make vitamins, antibiotics
• -food flavorings (yogurt, cheese)
• -DNA technology produce hormones like insulin

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Preventing bacterial infection

• Sterilization of surfaces (with antiseptics,
  heat, or steam)
• Cooling, freezing food
• Dehydrating food (salt curing)
• Use chemical preservatives (food or water
  chlorine)
• Radiation
• Pasteurization (heating liquids)
• Canning
• Washing hands!!!
• Antibiotics are used only AFTER have infection
  present

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Antibiotics vs. Antibodies vs. Antiseptics

• Antibodies produced by white blood cells in the
  body (internal line of defense) - can use
  vaccines
• Antibiotics kill bacteria using chemicals that
  are specific to bacteria metabolism and structure
• introduced IN TO body or ON TO site of
  infection as surface medication
• Antiseptics - Kill bacteria on OUTSIDE of body or
  on membranes that line areas leading to inside
  (ex. Mouth)
• Ex. Alcohol, Listerine, Iodine, Hydrogen
  Peroxide
• Disinfectants destroy bacteria/viruses on
  non-living surfaces
• Ex chlorox, bleach, lysol