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Bacteria v Virus
Structure of a Bacterial Cell
http://en.wikipedia.org/wiki/Image:Average_prokaryote_cell-_en.svg
Cell Wall
-maintains cell structure
-composed of peptidoglycan, a
polymer of sugars and amino
acids
Plasma Membrane
•phospholipid bilayer
Nucleoid
•The region DNA is found in
prokaryotes
•DNA
•A single double-stranded circular
chromosome
•NO histone proteins
Plasmid
•small circular chromosome
•may carry an antibiotic resistance
gene
Flagella
-tail-like structure used for
locomotion
Features of an Infectious Bacteria
• capsule: surrounds
bacterial cell wall; protects
bacteria from phagocytosis
• pili: allows bacteria to
attach to and invade other
cells despite mucous and
cell-turnover
• enzymes: break down
matrix between cells
allowing bacteria to spread
throughout tissues
Bacteria create Toxins
exotoxins:
cause lysis (breakage) of specific host cells
enterotoxins:
cause secretion of fluid into the small intestine
leading to vomiting and diarrhea
http://en.wikipedia.org/wiki/Image:Average_prokaryote_cell-_en.svg
endotoxins:
cell-bound lipopolysaccharides; causes fever and
inflammation
Fast Reproduction
• Bacterial Transcription
and Translation is
quicker then
eukaryotes
• Reproduction occurs
independent of host
cell
Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard
Bacterial Illness: Strep Throat
Infectious agent: Streptococcus pyogenes
spherical bacteria usually found in pairs or
chains
most sore throats are actually caused by viruses
and are NOT considered strep throat (~1535% are strep throat)
symptoms: sudden, severe sore throat, fever
over 101°F, swollen tonsils and lymph nodes,
white or yellow spots on the
back of a bright red throat
transmission usually by air-born bacteria
incubation period prior to symptoms 2-5 days
diagnosed with a throat culture and detection of
strep-specific molecules
treated with antibiotics, usually penicillin
for 10 days
Antibiotic Treatment of Bacterial Infections
• antibiotics kill bacteria or prevent bacteria from dividing
• antibiotics are produced naturally by bacteria and fungi
• antibiotics are mass produced by growing huge cultures of the source
microbe
Why might microbes produce antibiotics in nature?
Staphyloccocus
aureus
antibiotic
http://en.wikipedia.org/wiki/Image:Staphylococcus_aureus_%28AB_Test%29.jpg
Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.
Antibiotics: Mechanisms of Action
Inhibition of Bacterial Protein Synthesis
- some antibiotics bind to the large or small subunit of the
bacterial ribosome
Examples: neomycin,
streptomycin,
azithromycin,
erythromycin,
tetracycline
http://en.wikipedia.org/wiki/Image:Average_prokaryote_cell-_en.svg
ife Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard
College.
Antibiotics: Mechanisms of Action
Inhibition of Cell Wall Synthesis
-some antibiotics prevent peptidoglycan formation
Examples: vancomycin,
amoxicillin, ampicillin,
penicillin
e Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.
http://en.wikipedia.org/wiki/Image:Average_prokaryote_cell-_en.svg
Animation of Antimicrobial Resistance
Properties of Viruses
Basic Structure
• single stranded OR
double stranded RNA or
DNA
• protein shell capsid
• some have a lipid
bilayer with embedded
proteins
Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.
Host
Cell
Influenza
http://microbewiki.kenyon.edu/index.php/Image:8430_lores.jpg
Properties of Viruses
Virus Life Cycle and reproduction
virus attaches to host cell
• virus enters cell via endocytosis
• capsid degraded
• host transcribes viral DNA
• host ribosomes translate viral RNA
• new viruses assemble
Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard
Host
Cell
Viral Illness: The Common Cold
http://en.wikipedia.org/wiki/Image:Rhinovirus.PNG
• symptoms: sore throat, runny nose, nasal congestion, cough
• prevalance: 3 colds/ person/ year
incubation period 2-5 days
• no cure for the common cold (or the flu)
Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard
Rotavirus is a
virus that
causes
gastroenteritis
(inflammation of
the stomach and
intestines).
Bacterial vs. Viral Infections
Watch Video
Why don’t antibiotics work for viral infections?
MicrobeLibrary.org; © Jean-Yves Sgro, University of Wisconsin
Streptococcus
http://www.microbelibrary.org/microbelibrary/files/ccImages/Articleimages/simonson/Images/Streptococcus%20sobrinus%20fig1.jpg
Polio Virus
Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard
College.
Bacterial Infections
Viral Infections
• strep throat
• the flu
• gastroenteritis
• colds
• cholera
• AIDS
• tuberculosis
• hepatitis
• food poisoning
• chicken pox
• botulism
• gastroenteritis
• gangrene
• measles
• necrotizing fasciitis
• mumps
• boils, abscesses
• E. Bola
• pneumonia
• pneumonia
• acne
• West Nile
• meningitis
• cervical cancer
• ulcers
Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard
College.