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Topic A: Prokaryotes & Topic A: Prokaryotes & EukaryotesEukaryotes
Defining Defining features and features and
characteristicscharacteristics..
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OverviewOverview Differences that define prokaryotic
and eukaryotic cells
The three super kingdoms and distinctions between
archaea and bacteria as well as archaea and eukarya
Eukaryotic cellsEukaryotic cells
Defining features
Nucleus (membrane bound compartment housing genetic material)
Mitochondria/Plastids –other subcellular components
(Sapp, J. 2005)
Prokaryotic cellsProkaryotic cells
Defining features
Lack of membrane bound nuclear envelope
Lack of mitochondrion/plastids
Currently defined by an absence of eukaryotic characteristics
(Sapp, J. 2005) doi:10.1128/JMBR.69.2.292–305.2005
Prokaryotic Prokaryotic EukaryoticEukaryotic
Animal Liver cell Electron Micrograph
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E. Coli Electron Micrograph
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The Three Super KingdomsThe Three Super Kingdoms The three super kingdoms and
distinctions between archaea and bacteria as well as archaea and eukarya
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ArchaeaArchaea and and BacteriaBacteria
Classification methods
Phylogenetics (16S, 23S rRNA sequence)-current primary method of classification
Gram reaction (gram staining)-gram pos/neg Habitat (environment, symbiotic, syntrophic)-thermo, halo, acido Physiology (aerobic, anerobic)-methanogens (Schleifer, K. 2009)
Archaea Archaea andand Bacteria Bacteria (cont.)(cont.)
16S rRNA
Carl Woese began using the technique in the 70’s to build the phylogenetic tree we have today.1
Supported by another method based on content of genes rather than sequence (shared gene tree).2
1. (Doolittle, F. 1999) 2. (Snel, B., Bork, P., Huynen, M. 1999)
Archaea Archaea andand Bacteria Bacteria (cont.)(cont.)
Membrane lipids in archaea have ether bonds rather than ester bonds with possible branching.1
Some archaea fuse membrane lipids together to create a monolayer that is much stronger than a bilayer.2
-resistance to heat
Archaea cell walls do not contain peptidoglycan unlike their bacterial counterparts.3
-gram
2. (Hanford, M., Peeples, T. 2002)1. (De Rosa, M., Gambacorta, A., Gliozzi, A., 1986) 3. (Howland, J. 2000., p. 32)
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ArchaeaArchaea andand EukaryaEukarya
Similarly to archaea, eukarya that have a cell wall also lack peptidoglycan.1
-gram
Unlike archaea and similarly to bacteria, euykarya possess ester linkages in their phospholipids.2
-limited habitat2. (De Rosa, M., Gambacorta, A., Gliozzi, A., 1986)1. (Howland, J. 2000., p. 32)
Archaea and eukarya possess a relatively high number of RNAP subunits, at least 7 for archaea and eukarya compared to bacteria which only has 4 major subunits.
In transcription archaea and eukarya also share a TATA binding site. Leads to the befief that eukarya evolved from early archaea.
Archaea Archaea and and EukaryaEukarya
(Brown, J., Doolittle, F. 1997)
SummarySummary
The domains Prokaryotes and Eukaryotes are defined by morphological means.
This does not properly display ancestry.
SummarySummary Archaea are classified as being more
closely related to eukarya due to gene transcription similaraties.
Morphological classifications (i.e. structure and appearance) are useful for categorizing however it does not necessarily resemble phylogenetic relationships.
ReferencesReferences
Hanford, M., Peeples, T. (2002). Archaeal tetraether lipids Unique structures and applications, Applied Biochemistry and Biotechnology, 97(1), 45-62
Doolittle, F. (1999). Phylogenetic classification and the universal tree. Science. 284, 2124-2128
Snel, B., Bork, P., Huynen, M. (1999). Genome phylogeny based on gene content. Nature Genetics. 21, 108-110
Sapp, J. (2005). The Prokaryote-Eukaryote Dichotomy: Meanings and Mythology. Microbiology and molecular biology reviews, 69(2), 292–305. doi:10.1128/JMBR.69.2.292–305.2005
Schleifer, K. (2009). Classification of Bacteria and Archaea: Past, present and future. Systematic and Applied Microbiology, 32(8), 533-542. doi:10.1016/j.syapm.2009.09.002
De Rosa, M., Gambacorta, A., Gliozzi, A., (1986). Structure, biosynthesis and physiochemical properties of archaebacterial lipids. Microbiol. Rev., 50(1), 70-80
Howland, J. (2000). The Surprising Archaea: Discovering Another Domain of Life. Oxford: Oxford University Press.
Brown, J., Doolittle, F. (1997) Archaea and the Prokaryote-to-Eukaryote Transition. Microbiology and molecular biology reviews, 61(4), 456–502