Download Worked on Tobacco Mosaic Virus

Virus Objectives
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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
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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
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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
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Obligate aerobic bacteria must have
oxygen.
– Streptococcus
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Obligate anaerobes die if oxygen is
present.
– Clostridium
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Facultative anaerobes w/ or w/o
oxygen.
– E. coli
Reproduction
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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
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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