Download viruses? Bacteria

Bacteria & Viruses
What are the characteristics of viruses?
Bacteria? What kingdom do each of
these belong? Are they living? Why or
why not?
• Kingdoms
– Eukar
What do you already know?
• What are the differences between
viruses and bacteria?
• Are all bacteria harmful?
• When you get a cold, should you
take an antibiotic to help you get
better?
• What’s the best and easiest thing
to do to avoid getting sick?
• Bacteria Video
Bacteria
• Bacteriology is the study of bacteria
• Bacteria are prokaryotic, unicellular
organisms containing DNA and ribosomes.
• Bacteria have ALL the characteristics of living
things.
• Bacteria have the greatest percentage of the
biomass on Earth!
Bacterial Structure
• Basic structure of bacteria:
Peptidoglycan*
Cell
wall
Flagellum
Cell
Ribosome
membrane
DNA
Pili
Bacterial Structure
• Bacteria have three distinct shapes:
spherical
(cocci)
rod-shaped
(bacilli)
spiral
(spirilla)
• Are bacteria harmful or useful?
Bacteria
• Bacteria have a variety of important uses:
– Help make interesting food (buttermilk, yogurt, cheese,
sauerkraut, pickles, and olives, etc…)
– Decompose organic matter (recycle nutrients from dead
organisms; break down sewage into simpler compounds)
– Nitrogen fixation (chemically changes nitrogen gas, N2,
into ammonia, NH3, so plants can make amino acids)
– Human health (bacteria on skin help prevent infection &
bacteria in gut helps digest food & make vitamins)
– Biotechnology (used to make antibiotics, insulin, human
growth hormone, vitamins, and other drugs)
How Do Pathogenic Bacteria Work?
Bacteria produce disease in one of two ways:
• Using cells for food: The bacteria break down
healthy cells for food, destroying tissues
• Releasing toxins: The bacteria produce a
toxin (poisonous protein) that is released into
the bloodstream where it can travel
throughout the body, disrupting normal
activity and damaging tissues
Bacteria
• A rather vocal minority (less than 1%) of
bacteria cause disease in humans, animals, and
plants.
• Bacteria can cause a variety of diseases:
–
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–
–
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Food Poisoning
Tuberculosis
Cholera
Syphilis
Ulcers
Strep Throat
– Scarlet Fever
– Whooping Cough
– Bacterial Meningitis
– Pneumonia
– Leprosy
– Tetanus
VIDEO CLIP:
Understanding
Bacteria
Viruses
Living or Nonliving?
Viruses
 Virology is the study of viruses
 Viruses are “biological entities” containing
either DNA or RNA that require another
cell to survive.
 Viruses have some, but not all, of the
characteristics of life.
*So are viruses living or non-living?*
 Viruses seem to exist only to make more
viruses!
Viral Structure
• All viruses have the same basic structure:
Capsid (Protein
coat)
Nucleic acid
core (DNA or
RNA)
How Do Viruses Work?
 In order to replicate and make copies of itself,
viruses need a host cell. Any living cell can
become a host cell (human, animal, plant, and
even bacterial cells!)
 Without a host cell, viruses cannot function (i.e.are harmless!)
 Although any cell can theoretically become a host
cell, specific viruses will only infect specific cells
(EX: HIV will only infect human T cells, a part of your
immune system)
How Do Viruses Work?
• Attach: The capsid of the virus binds to receptor
proteins on the surface of a host cell, tricking the host
cell into thinking it’s not a foreign invader.
• Inject: The virus then injects its genetic material (DNA
or RNA) into the host cell.
• Assemble: The viral genes are expressed, turning the
host cell into a virus-making factory.
• Repeat: The host cell eventually bursts, releasing the
hundreds of newly formed viruses to infect surrounding
cells!
VIDEO CLIP:
How Viruses Work
Viruses
• Viruses can cause disease in humans, animals, plants,
and even bacteria!
• Viruses can cause a variety of diseases:
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Common cold
Hepatitis A, B & C
Herpes
Mononucleosis
Warts
Chickenpox
– Polio
– Influenza
– Mumps
– Measles
– Viral Meningitis
– AIDS
VIDEO CLIP:
Viral Disease
Protection
• There are a few big ways to protect yourself
against pathogens (disease causing agents)
– Antibiotics (drugs to kill bacteria)
– Antivirals (drugs to treat viruses)
– Vaccination (using your body’s own immune
system to preemptively guard against attack)
Antibiotics
• Antibiotics can only be used to treat bacterial
infections!
• Target specific structures on bacteria to kill them.
• First made from a fungus (penicillin), now most
are made artificially.
• Unfortunately, antibiotic resistance (where the
antibiotic doesn’t kill the target bacteria anymore)
is becoming a major problem.
Antivirals
• Antivirals can only be used to treat certain viral
infections!
• Does not “kill” or disarm the virus permanently; only
shortens symptoms by 1-2 days.
• Usually only prescribed to patients with life
threatening symptoms or those that have a greater
chance of developing complications (because of their
age or they have a high-risk medical condition).
• Just like antibiotics, there is evidence of antiviral
resistance too!
Vaccination
• Vaccines can only be used to prevent infections
(both viral and bacterial) from leading to disease.
• “Trick” your immune system to make antibodies
that destroy foreign “bodies” or particles (such as
bacteria and viruses). Your body remembers how to
make these antibodies when the real thing invades.
• Made from a weakened virus, inactivated virus, or
by using only part of the virus/bacteria itself.
VIDEO CLIP:
Vaccination
Viruses and the flu
To Review....
 What are the differences between viruses
and bacteria?
 Are all bacteria harmful? Explain.
 When you get a cold, should you take an
antibiotic to help you get better? Why?
 What’s the best and easiest thing to do to
avoid getting sick?
http://www.youtube.com/watch?v=3xRttWuf3
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Bacteria
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