THE PROKARYOTES
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Transcript of THE PROKARYOTES
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Domains & Dogma
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Systematics of Prokaryotes• Focus on animals and plants
– History limited to 20% of evolutionary time
• How to classify prokaryotes?
Limited in morphological characters
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Gram Stain and Structure
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rRNA unlocks the domains
Zuckerkandl and Pauling
Emile Zuckerkandl (1922-2013); Austria & USA. Molecular biology and molecular clock
Linus Carl Pauling (1901-1994) USA Founder of fields like quantum chemistry and molecular biology
Suggested that a tree of life might be generated by comparing sequences of biopolymers like RNA
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Ribosomal Structure
Two subunits
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Ribosomal subunits=rRNA molecules + proteins
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Prokaryotes Eukaryotes
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What’s the ‘S’?
• Svedberg units: a measure of how quickly particles sediment in an ultracentrifuge
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What’s the ‘S’?• Svedberg units: a measure of how
quickly particles sediment in an ultracentrifuge
• Larger the particle, the greater its S value
• Smaller subunit of a ribosome sinks slower than the larger subunit
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Why then does 5S + 23S = 50S?
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Why then does 5S + 23S = 50S?
Shape AND size determine sedimentation rate…
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Ribosomal RNA Molecules
• Components of the ribosomes of ALL ORGANISMS
• Changes in rRNA nucleotide sequence indicative of evolutionary history
SSU rRNA
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Carl Richard Woese
1928-2012, USA; Developed system based on 16S rRNA in 1977
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Carl Woese and George Fox 1977
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A modification of Woese et al. (1990) from Brock et al. (1994).
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Eubacteria
>9 KingdomsSame type of ribosomesPolysaccharide of outer wall made of MureinMost groups involved in global nutrient cyclingMany of economic importanceDiseaseOther functions (e.g. antibiotic producers)
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Archaea• Differ from the Eubacteria
– Form of ribosomes– No murein– Different lipids– Different RNA polymerase
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Two different supertrees generated by ML methods for complete genomes of 45 taxa. Daubin et al. 2002
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Ciniglia et al. 2004
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Lang et al. 2013Using 24 genes and 3000 taxa
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Raymann et al. 2015
Support for a two- domain system. Eukayotes arose from within the Archaea and sister to the Lokiarchaeota.
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Spang et al. 2015
Colored dots indicate distribution of Eukaryotic Signature Proteins
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Forterre 2015pg=peptidoglycan
LUCA=Last universal common ancestor
LBCA=Last bacterial common ancestor
LACA=Last archaeal common ancestor
LARCA=Last Arkarya common ancestor
FME=First mitochondriate eukaryote
LECA=Last eukaryotic common ancestor
SARP=Stramenopiles, alveolates, rhizobians, plantae
Figure 3. Schematic universal tree updated from Woese et al. (1990)
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Three Domains
Eukaryotes Early
Eocyte
Ring of Life
Modified from McInerney et al. 2015
Argued that the domain concept was indefensible because eukaryotes are not monophyletic unless we consider all of life
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Life’s history is complex and we should not try to simplify it to suit our need for orderly nomenclatural systems.
-McInerney et al. 2015