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” in Latin.
• 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
• All viruses are:
– Small – 20nm (polio virus) – 350nm (small pox virus)
– Single type of nucleic acid (RNA or DNA but never
both)
– Have a 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
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, get replicate and get out to invade other host cells
• The cold, the flu, Rubella (German measles), mumps
Release
Attachment at Receptor site
Entry
Replication
Assembly
The Lytic Cycle of 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
• HIV, cold sores, chicken pox, hepatitis
Prophage
Attachment
& Injection
Integration
of nucleic acid
Cell multiplication
Prophage remains unnoticed and not transcribed. If animal cells, then its called a
Provirus such as with all the herpes viruses and HIV (HIV+)
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
GLEN!!
Polio
• Vaccines (SHOTS!!) are small doses of
either killed, altered or live viruses. Body
builds up antibodies against viral proteins.
Polio and the Iron Lung
The Different forms of Viruses
• Retroviruses – HIV. Contains RNA instead of DNA.
Goes from RNA to DNA to RNA to protein. Normal
is DNA to RNA to protein.
• 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.
Bacteria
• Eubacteria &
Archaebacteria
– 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
• Extremophiles
• On the same line of evolution as
eukaryotes
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
Basic Structure
BACTERIA SONG
Endospores
• Produced by Gram + (usually Bacillus
& Clostridium)
• Dormant structure to survive adverse
conditions (heat, cold, dryness).
Bacillus anthracis
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Reproduction
Asexually by binary
fission. No genetic
variation
Conjugation - Sexual
reproduction method .
Two bacteria form a
conjugation bridge or
tube between them.
DNA is transferred from
one bacteria to the other
Binary Fission and Conjugation
Bacteria and Humans
• Pathogens – disease causing agents
(Pathology – science of studying
diseases)
• Can produce poisonous toxins
(poisons) like the botulism toxin
• Destroy food crops
• Food poisoning
To fight them:
• Antibiotics interfere with the
production of the cell wall or
protein or DNA synthesis.
Penicillin, tetracycline
• Bacteria can mutate and
become antibiotic resistant
(often results from overuse of
antibiotics)
– Usually due to conjugation or
Transformation
Partners
Area Tested
# of Colonies
22`C
37`C
# of Varieties
Partners
Area tested
# of colonies
# of varieties
Partners
Area tested
# of colonies
# of varieties
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