Virus Objectives What is a virus? What is the structure of a typical virus? How do viruses...
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Transcript of Virus Objectives What is a virus? What is the structure of a typical virus? How do viruses...
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Virus Objectives
• What is a virus?
• What is the structure of a typical virus?
• How do viruses reproduce?
• C/C lytic and lysogenic cycles
• What happens to viruses once they infect
an organism?
* Name some viruses and what they do
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History
• Iwanowski and Beijernick (1890’s) – Worked on Tobacco Mosaic Virus (infects tobacco and
tomato leaves). – Creates mosaic pattern on leaves. – Made a juice of the infected leaves and then put this
juice through a filter. • Rubbed the filtered juice onto leaves. • Still became infected. • Concluded that whatever these disease causing
particles were, they were very small (smaller than bacteria).
• Named them viruses meaning “poison”.
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• Stanley (1935) – Purified TMV into a
crystal. – Living particles don’t
crystallize therefore, viruses are non-living pathogenic (disease causing) particles.
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Viruses• Particles of nucleic acid, protein and
sometimes a lipid envelope.
• Obligate intracellular parasite (can only replicate within a living cell)
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Structure of a virus
• Small – 20nm (polio virus) – 350nm (small pox virus)
• Single type of nucleic acid (RNA or or DNA but never both)
• Protein coat – capsid• Some have envelopes (made of lipids)outside
of capsid• Surface projections made up of lipids for
attachment onto host cells• Are specific to their host
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Shapes
• Shapes are – Rod– Helical– Icosahedral (20 sides)
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HIVRetrovirus
Envelope Projections
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Bacteriophage
Infect E. coli bacteria
Attach with tail fibers onto cell.
Inject nucleic acid into cell
Capsid
Tail
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The Lytic Cycle • Get in, replicate and get out to invade other host cells• Virulent (Disease causing)• The cold, rubella (German measles), mumps
ReleaseAttachment at Receptor site
Entry
Replication
Assembly
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The Lytic Virus infection
Attaches onto host cell Injects DNA into host cell Replication of Viral parts
Reassembly of virons Lysis – bursting out
Viruses that reproduce only by the lytic cycle are called Virulent
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Lysogenic InfectionLysogenic Infection• Virus embeds its DNA into hosts DNA which is
replicated with host cell’s DNA. • Remains unnoticed for sometimes years• AIDS, cold sores, chicken pox, hepatitis
Prophage
Attachment Integration Cell multiplication & Injection of nucleic acid Prophage remains unnoticed and not transcribed
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Viral Diseases • Measles, Mumps, Rubella, Rabies, the Cold,
the Flu, Influenza, Hepatitis, AIDS, Chicken pox, Small pox, Polio, Yellow fever, Meningititis, some cancers, Swine flu
• Vaccines are small doses of either killed, altered or live viruses. Body builds up antibodies against virus
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Diseases caused by viruses
• AIDS• The Cold• Measles• Mumps• Rubella• Chicken pox/Shingles• Small Pox• Hepatitis• SARS• The Flu• Ebola• HPV• Bird Flu• Polio
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The Different forms of Viruses• RetrovirusesRetroviruses – AIDS. Contains RNA instead
of DNA. Goes from RNA to DNA to RNA to protein. Normal is DNA to RNA to protein.
• ViroidsViroids – another disease causing agent but no capsid, only the RNA. – Found only in plants
• PrionPrion – viral proteins that cause diseases. Scrapie in sheep degrades nervous system. Mad Cow disease (Bovine spongiform encephalopathy) in cows – puts holes into brain.– In humans, its Creutzfeld-Jakob disease & Kuru.
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Bacterial Objectives• What are the two bacterial
kingdoms/domains? How are they different?• Describe the structure of a typical bacterial
cell and the 3 main shapes• How do bacteria reproduce and metabolize?• Name some common bacterial disease and
their causative agents.• How are bacteria important to us?
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• Formally known as Kingdom – Monera
• Unicellular,
• Prokaryotic cell (no nucleus or membrane bound organelles.
• Have Ribosomes and a cell wall ,
• Single long, circular strand of DNA
• Auto or Heterotrophic
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Kingdom – ArchaebacteriaKingdom – Archaebacteria
• Lack Peptidoglycan in cell wall – a sugar/protein substance
• Extremophiles
• First organisms to colonize primitive earth
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Kingdom – EubacteriaKingdom – Eubacteria• Larger of the two kingdoms
• Have Peptidoglycan in cell wall
• 3 basic shapes
– Bacilli – Rod shaped. E. coli, Bacillus anthracis
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– Cocci – Spherical shaped. • Staphylococcus aureus, Streptococcus pyogenes
Strepto – Chains Tetra - 4 Staphylo –clusters• Diplo – 2
• Spirilla – Spiral shaped. Spirochette, Syphilis
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Staining properties • Groups Eubacteria in two groups
– Gram Staining• Gram Positive – Gram stain purple with Crystal
violet due to thick layer of peptidoglycan. Easier to kill with antibiotics
• Gram Negative – Gram stain pink with Safarin. Hard to kill with antibiotics due to thin layer of peptidoglycan
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Basic Structure
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EndosporesEndospores
• Produced by Gram + (usually Bacillus & Clostridium)
• Dormant structure to survive adverse conditions (heat, cold, dryness).
Bacillus anthracis
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Methods of Respiration
• Obligate aerobic bacteria must have oxygen.
– Streptococcus
• Obligate anaerobes die if oxygen is present.
– Clostridium
• Facultative anaerobes w/ or w/o oxygen.
– E. coli
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Reproduction
• Asexually by binary fission
• Conjugation - Sexual repro method . Two bacteria form a conjugation bridge or tube between them. DNA is transferred from one bacteria to the other
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Bacteria and Humans
• Pathogens – disease causing agents (Pathology – science of studying diseases)
• Can produce poisonous toxins (poisons) like the botulism toxin
• Destroy food crops
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To fight them:
• Antibiotics interfere with cell wall or protein synthesis. Penicillin, tetracycline
• Bacteria can mutate and become antibiotic resistant (often results from overuse of antibiotics)
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Helpful Bacteria:
1. Bacteria of decay - major decomposers (Saprophytes)
2. Symbiosis – Nitrogen Fixing bacteria - Convert atmospheric N2 to NH3, Rhizobium in root nodules of legumes
3. Fermentation: Food processing of sour cream, yogurt, buttermilk, wine, sauerkraut, pickles, cheese
4. Industrial – “oil eating bacteria”, mining gold, cleaning up pollutants - Bioremediation
5. Biotechnology
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Diseases caused by bacteria
• Anthrax• Botulism• Cholera• Cavities• Gonorrhea• Syphilis• Tetanus• Staph Infection (MRSA)• Food Poisoning• Lyme Disease• Diphtheria• Tuberculosis• Escherichia coli O157: H7• Leprosy• Meningitis• Strep throat• Whooping cough (Pertussis)
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Food poisoningFood poisoning • Results from decay of foods and
production of toxins
• 33 million people/yr get “stomach flu”
• Seafood accounts for 20 – 25% of cases
• 33% of all raw poultry tests + for Staphylococcus
• 1 in every 200 eggs has Salmonella
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4 C’s of Food Safety
Chill your foods
Cook your food to the proper
temperature
Clean food and cooking surfaces
Combat Cross Contamination
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Antibacterial AgentsAntibacterial Agents
• Antibiotics – organic substance that inhibits growth in/on living material. Penicillin
• Disinfectants – inhibits growth on a non-living surface – bleach, ammonia
• Antiseptics– inhibits growth on a living surface – alcohol, hydrogen peroxide
• Sterilization – high heat or chemicals that kills bacteria
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Antimicrobial agentsAntimicrobial agents
• DisinfectantsDisinfectants– 1 – Bleach– 2 – Ammonia– 3 – 409– 4 – Sterile water
• AntisepticsAntiseptics– 1 – Hand gel– 2 – Iodine– 3 – Alcohol– 4 – Sterile water
• AntibioticsAntibiotics– 1 – Streptomycin– 2 – Erythromycin– 3 – Tetracycline– 4 – Sterile water
• Bacteria Bacteria (indicate which on you have on your lab)– Bacillus cereus– E. coli– Serratia marcescens
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Antiseptic CCDisinfectant CC Antibiotic CC