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Prokaryotic Domains: Bacteria, Archaea and Viruses, Summaries of Nutrition

An overview of the prokaryotic domains, including bacteria with their various structures and differences between species, archaea and their extreme environments, and viruses with their structure and reproductive cycles. It also covers pathogenic bacteria and viruses, as well as the concept of emerging viruses and viral vaccines.

What you will learn

  • What are the three main types of bacterial structures?
  • How do archaea differ from bacteria?
  • What is the role of viruses in the environment and in human health?

Typology: Summaries

2021/2022

Uploaded on 09/12/2022

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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
Nitrogen fixing bacteria
Live in the soil
Help legumes (beans)
trap nitrogen
Bacteria are recyclers
Decompose organic
matter
Releases nutrients back
into the environment
Clean up pollution
(bioremediation)
Break down a lot of
chemicals
A hot area of research for
oil spills.
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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

  • Nitrogen fixing bacteria

Live in the soil

Help legumes (beans) trap nitrogen

Bacteria are recyclers

  • Decompose organic

matter

Releases nutrients back into the environment

  • Clean up pollution

(bioremediation)

Break down a lot of chemicals

A hot area of research for oil spills.

Pathogenic bacteria

  • Pathogenic: produces

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?

  1. Mutation of existing viruses RNA viruses: very high mutation rate
  2. “Jumping” species Frequently involve swine or birds
  3. 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.