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Diversity of Bacteria, Archaea, and
Viruses
Chapter 19
The prokaryotic domains
- Bacteria Three types of structure Spherical, rod-shaped, and spiral
- Archaea Many are extremophilic Prefer to live in very extreme environments.
Prokayotes (bacteria)
- Differences between species include
Size (range from 0.2 mm to 700 mm).
Shape (rod, spherical, spiral)
Gram stain results Gram negative
Gram positive
Presence or absence of flagellum.
Anaerobic vs aerobic
Prokaryotes and animals
- Prokaryotes are important
for animal nutrition
Herbivores need bacteria to digest cellulose
Humans need bacteria to make Vitamin K & vitamin B12.
Termites need bacteria to digest wood.
Bacteria and plants
Live in the soil
Help legumes (beans) trap nitrogen
Bacteria are recyclers
matter
Releases nutrients back into the environment
(bioremediation)
Break down a lot of chemicals
A hot area of research for oil spills.
Pathogenic bacteria
disease.
Many anaerobic bacteria cause disease Botulism, tetanus
Bubonic plague (black death)
Leprosy
Tuberculosis
A virus is a nucleic acid molecule with a
protein coat.
A. Structure of Viruses: Infectious particles consisting of: Nucleic acid genome (DNA or RNA) Protein coat = capsid Lipid bilayer = envelope
Capsids and Envelopes
Main capsid types:
- Polyhedrons
- Helical (rods)
Envelopes
Contain membrane glycoproteins: Bind to specific host cell protein = “viral receptor”
remember that glycoproteins act as identifying signals.
Features of viral reproductive cycles
Parasite : an organism (?) that benefits by living in or on
another organism (its host) at the expense of that organism.
Viruses cannot reproduce without a host cell.
No way to undergo mitosis or meiosis.
Obligate intracellular parasites
Viruses require from hosts:
- enzymes
- ATP
- ribosomes, etc.
- monomers (NTs, amino acids)
Rabies virus
Ebola virus
Concept 18.2 - Viruses, viroids and prions
are formidable pathogens
A. Viral diseases in animals /
emerging viruses.
Pathogenic virus: a disease- causing virus
Emerging viruses: sudden appearance (or sudden medical importance)
Examples: Avian bird flu
Where do emerging viruses come from?
- Mutation of existing viruses RNA viruses: very high mutation rate
- “Jumping” species Frequently involve swine or birds
- Spread from small isolated populations
Viral vaccines
Viruses or viral components used to stimulate immune system defenses (without causing the disease).
- Major types: Live (weakened) virus Polio virus, measles, mumps
Killed virus Flu shots, hepatitis A
Viral protein(s) Human papilloma virus (HPV)
Humans: H1N1 - 1918 “Spanish flu” H2N2 - 1957 “Asian flu” H3N2 - 1968 “Hong Kong flu” H5N1 - 2005 “Avian flu”
Transmission of influenza A
All flu viruses originate in aquatic
birds (= reservoir)
Why are we
fearful about
H5N1 (avian flu)?
1. Avian H5N1 in humans is highly
pathogenic.
But not easily transmitted: Poultry to human
Human to human
Immunity (^) No immunity
2. Humans would have little/no
immunity to this strain.
HA (a foreign protein)
What makes a particular strain pathogenic?
Unknown!Unknown! Unknown!Unknown!
1918 strain (Spanish flu) - “resurrected”
Pathogenic viruses
- Smallpox Oldest known viral disease First records in 150 A.D.
Disastrous for North American natives Why?
- World-wide vaccination helped
to nearly eradicate smallpox.
Two known repositories Atlanta, Georgia Russia
Pathogenic viruses
- Human papilloma virus Almost all cases of cervical cancer is due to HPV.
Cervical cancer survival rate has improved with pap smears and other screening. Stage 1: 80 – 90% survive Stage 2: 50 – 55% survive Stage 3: 15 – 25% survive
- HPV is sexually transmitted.
Pathogenic viruses
- Mumps and measles Mumps is not deadly But can cause sterility, especially in infected adult men.
Measles is highly contagious 90% of exposed people will develop measles.
German measles (rubella) in pregnant women will cause serious birth defects in fetus
Consuming prion-infected tissue (mostly neural)
Transmission of BSE (^) Prion disease transmission
- Kuru Occurred in New Guinea among the Fore tribe.
Medical puzzle that stumped researchers because it affected mostly women and children.
Mystery solved in the 1950s when it was discovered that the Fore tribe was cannibalistic, eating their dead relatives’s brains as a funeral rite.
