Post on 11-Jan-2016
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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
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”.
• Stanley (1935) – Purified TMV into a
crystal. – Living particles don’t
crystallize therefore, viruses are non-living pathogenic (disease causing) particles.
Viruses• Particles of nucleic acid, protein and
sometimes a lipid envelope.
• Obligate intracellular parasite (can only replicate within a living cell)
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
Shapes
• Shapes are – Rod– Helical– Icosahedral (20 sides)
HIVRetrovirus
Envelope Projections
Bacteriophage
Infect E. coli bacteria
Attach with tail fibers onto cell.
Inject nucleic acid into cell
Capsid
Tail
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
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
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
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
Diseases caused by viruses
• AIDS• The Cold• Measles• Mumps• Rubella• Chicken pox/Shingles• Small Pox• Hepatitis• SARS• The Flu• Ebola• HPV• Bird Flu• Polio
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.
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?
• 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
Kingdom – ArchaebacteriaKingdom – Archaebacteria
• Lack Peptidoglycan in cell wall – a sugar/protein substance
• Extremophiles
• First organisms to colonize primitive earth
Kingdom – EubacteriaKingdom – Eubacteria• Larger of the two kingdoms
• Have Peptidoglycan in cell wall
• 3 basic shapes
– Bacilli – Rod shaped. E. coli, Bacillus anthracis
– Cocci – Spherical shaped. • Staphylococcus aureus, Streptococcus pyogenes
Strepto – Chains Tetra - 4 Staphylo –clusters• Diplo – 2
• Spirilla – Spiral shaped. Spirochette, Syphilis
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
Basic Structure
EndosporesEndospores
• Produced by Gram + (usually Bacillus & Clostridium)
• Dormant structure to survive adverse conditions (heat, cold, dryness).
Bacillus anthracis
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
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
Bacteria and Humans
• Pathogens – disease causing agents (Pathology – science of studying diseases)
• Can produce poisonous toxins (poisons) like the botulism toxin
• Destroy food crops
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)
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
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)
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
4 C’s of Food Safety
Chill your foods
Cook your food to the proper
temperature
Clean food and cooking surfaces
Combat Cross Contamination
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
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
Antiseptic CCDisinfectant CC Antibiotic CC