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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 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) HIV Retrovirus Envelope Projections Bacteriophage Capsid Infect E. coli bacteria Tail Attach with tail fibers onto cell. Inject nucleic acid into cell The Lytic Cycle • Get in, replicate and get out to invade other host cells • Virulent (Disease causing) • The cold, rubella (German measles), mumps Release Attachment at Receptor site Entry Assembly Replication The Lytic Virus infection Attaches onto host cell Injects DNA into host cell Reassembly of virons Replication of Viral parts Lysis – bursting out Viruses that reproduce only by the lytic cycle are called Virulent Lysogenic 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 & Injection Integration of nucleic acid Cell multiplication Prophage remains unnoticed and not transcribed Lytic and Lysogenic Cycles 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 Polio and the Iron Lung The Different forms of Viruses • Retroviruses – AIDS. Contains RNA instead of DNA. Goes from RNA to DNA to RNA to protein. Normal is DNA to RNA to protein. • Viroids – another disease causing agent but no capsid, only the RNA. – Found only in plants • Prion – 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 – Archaebacteria • Lack Peptidoglycan in cell wall – a sugar/protein substance • Extremophiles • First organisms to colonize primitive earth Kingdom – 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 Diplo – 2 Staphylo –clusters • 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 Endospores • 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 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 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 agents • Disinfectants – 1 – Bleach – 2 – Ammonia – 3 – 409 – 4 – Sterile water • Antibiotics – 1 – Streptomycin – 2 – Erythromycin – 3 – Tetracycline – 4 – Sterile water • Antiseptics – 1 – Hand gel – 2 – Iodine – 3 – Alcohol – 4 – Sterile water • Bacteria (indicate which on you have on your lab) – Bacillus cereus – E. coli – Serratia marcescens Antiseptic CC Disinfectant CC Antibiotic CC