Topic A: Prokaryotes & Topic A: Prokaryotes & EukaryotesEukaryotes

Defining Defining features and features and

characteristicscharacteristics..

Image retrieved from: http://www.featurepics.com/online/Cells-624015.aspx

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

Image retrieved from: http://www.ibguides.com/biology/notes/2.3-eukaryotic-cells

E. Coli Electron Micrograph

Image retrieved from: http://www.ibguides.com/biology/notes/2.2-prokaryotic-cells

The Three Super KingdomsThe Three Super Kingdoms The three super kingdoms and

distinctions between archaea and bacteria as well as archaea and eukarya

Image retrieved from: http://www.jamstec.go.jp/e/about/press_release/20080722/

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)

Image retrieved from: http://202.204.115.67/jpkch/jpkch/2008/wswx/chapter%2011.htm

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