2/4/15 1 Prokaryotes (Domains Bacteria & Archaea) KEY POINTS 1. Decomposers: recycle organic and inorganic molecules in environment; makes them available to other organisms. 2. Essential components of symbioses. 3. Encompasses the origins of metabolism and metabolic diversity. 4. Origin of photosynthesis and formation of atmospheric Oxygen Animals Colonization of land Paleozoic Meso- zoic Humans Ceno- zoic Origin of solar system and Earth Prokaryotes Proterozoic Archaean Billions of years ago 1 4 3 2 Multicellular eukaryotes Single-celled eukaryotes Atmospheric oxygen ANTIQUITY • >3.5 BILLION years old. • Alone for 2 billion years General characteristics 1. Small: compare to 10-100µm for eukaryotic cell; single-celled; may form colonies. 2. Lack membrane- enclosed organelles. 3. Cell wall present, but different from plant cell wall. 0.5-5µm
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Prokaryotes (Domains Bacteria & Archaea)
KEY POINTS 1. Decomposers: recycle organic and
inorganic molecules in environment; makes them available to other organisms.
2. Essential components of symbioses. 3. Encompasses the origins of metabolism and
metabolic diversity. 4. Origin of photosynthesis and formation of
atmospheric Oxygen
Animals
Colonization of land
Paleozoic Meso-
zoic Humans
Ceno- zoic
Origin of solar system and Earth
Prokaryotes Proterozoic Archaean Billions of years ago
1 4
3 2
Multicellular eukaryotes
Single-celled eukaryotes
Atmospheric oxygen
ANTIQUITY
• >3.5 BILLION years old.
• Alone for 2 billion years
General characteristics 1. Small: compare to
10-100µm for eukaryotic cell; single-celled; may form colonies.
2. Lack membrane-enclosed organelles.
3. Cell wall present, but different from plant cell wall.
0.5-5µm
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General characteristics
4. Occur everywhere, most numerous organisms.
– More individuals in a handful of soil then there are people that have ever lived.
– By far more individuals in our gut than eukaryotic cells that are actually us.
General characteristics
5. Metabolic diversity established nutritional modes of eukaryotes.
General characteristics
6. Important decomposers and recyclers
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General characteristics
6. Important decomposers and recyclers • Form the basis of
global nutrient cycles.
General characteristics
7. Symbionts!!!!!!! • Parasites • Pathogenic
organisms. • About 1/2 of all
human diseases are caused by Bacteria
General characteristics
7. Symbionts!!!!!!! • Parasites • Pathogenic
organisms. • Extremely important
in agriculture as well.
Pierce’s disease is caused by Xylella fastidiosa, a Gamma Proteobacteria. It causes over $56 million in damage annually in California. That’s with $34 million spent to control it! = $90 million in California alone.
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General characteristics
7. Symbionts!!!!!!! • Commensalists • They are
everywhere (really). • There can be 10
million cells per square centimeter of skin.
General characteristics
7. Symbionts!!!!!!! • Mutualists • Eukaryotic life
would be impossible without this.
General characteristics 7. Symbionts!!!!!!!
• Mutualists • Allows herbivorous
(plant-feeding) animals to digest cellulose and other low-quality plant tissues.
• Termites • Ungulates “chewing the
cud” • Lagomorph coprophagy
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General characteristics 7. Symbionts!!!!!!!
• Mutualists • Mealybug endosymbionts
with endosymbionts.
General characteristics 7. Symbionts!!!!!!!
• Mutualists • Komodo dragons and their “toxins”.
• Hunt large prey and can inflict fairly minor wound.
• Prey die fairly quickly from wound.
• Infection by highly pathogenic Pasteurella multocida (Gamma Proteobacteria).
• Prominent in saliva of dragons, but dragons have an anti-Pasteurella antibody.
TAXONOMY is problematic
• Relationships obscured by billions of years of evolution
• Also obscured by unique bacterial means of recombination (more later).
• Grouped primarily by DNA sequence data.
• Immense genetic/genomic diversity.
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Current taxonomy is stabilizing
• Note that “Prokaryote” is paraphyletic. Why?
• Two Domains: • Archaea: extremophiles
(mostly), ancient, probable progenitors of eukaryotes.
• Bacteria: most commonly-encountered prokaryotes.