Download doc MIMM 211 Lecture Notes 3

MIMM 211 Lecture 3
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CLASSIFICATION OF MICROBES
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Traditional (before 1866)
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Plants and Animals
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Haeckel's Proposal (After 1866)
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Plants, Animals, Microorganisms
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Edouard Chatton (1937)
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Eukaryotes and Prokaryotes
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Roger Stainer and C.B. Van Niel supported Chatton's proposal
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RECENT CLASSIFICATIONS
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Whitaker's Five Kingdoms (1959)
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Monera, Protista, Fungi, Plantae, Animalia
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Wrong
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Carls Woesse's THREE KINGDOMS-- or THREE DOMAINS (1977)
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Bacteria, Archaea, and Eukarya
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Used molecular approach, 16S ribosomal RNA gene used (Ubiquitous)
16S could not be easily transferred during horizontal gene transfer (HGT)
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ENDOSYMBIOTIC THEORY OF EVOLUTION
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Theory developed by Lynn Margulis (1981)
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Prokaryotes
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No organelles
Eukaryotes
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Organelles
Plants have mitochondria and chloroplasts
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Most others only have mitochondria
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Has nuclear envelope
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Mitochondria and Chloroplasts
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Almost the same size
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Contain circular DNA (active genome)
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Contain 70s ribosome (instead of 80s in eukaryotes)
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Have double membrane (like gram negative bacteria), but no cell envelope
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Divide by binary fission (reproduce separately from host)
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Mitochondria descend from gram-negative proteobacteria Rickettsia prowazekii
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Obligate intracellular parasite, cannot live outside host
Chloroplasts descend from cyanobacteria Prochloron
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Theory:
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Prokaryotes first appeared 3.5 mya
Eukaryotes, 1 mya
Primitive Eukaryote engulfed prokaryote
Continued to develop a mutually beneficial symbiotic relationship for 1 bya
Prokaryote is in a stable, sheltered, nutrient-rich environment
Eukaryote gets ATP from photosynthesis and respiration
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RECENT EXAMPLE
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Aphids and endosymbiont (200 mya)
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Endosymbiont kept cell envelope
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Endosymbiont can't survive outside host
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Aphid dies is endosymbiont is killed by antibiotic
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Endosymbiont closely related to e. coli