Comparisons of Eubacteria, Archaea, and Eukaryotes

Characteristic	Eubacteria	Archaea	Eukaryotes
Cell wall	gram +ve or gram -ve (structure)	murein absent	plasma membrane
Predominantly multicellular	no	no	yes
Nucleus, membrane bound organelles	no	no	yes
DNA	circular	circular	linear
Ribosome	70s	70s	80s
Membrane lipids ester-linked*	yes	no	yes
Photosynthesis with chlorophyll	yes	no	yes
Growth above 80o C	yes	yes	no
Histone proteins present	no	yes	yes
tRNA initiator	fMet	Met	Met
Operons	yes	yes	no
Introns in genome	none	some [a, 1, 2, 3, 4, 5, 6, 7, 8,]	most
Capping and poly-A tailing of mRNA	no	no	yes
Transcription factors required	yes	no	yes
Methanogenesis	no	yes	no
Nitrification	yes	no	no
Denitrification	yes	yes	no
Nitrogen Fixation	yes	yes	no
Chemolithotrophy	yes	yes	no
Gas vesicles present	yes	yes	no
Sensitive to chloramphenicol, kanamycin and streptomycin	yes	no	no
* Archaea membrane lipids are ether-linked
Adapted from here.

Property	Eubacteria	Archaea	Eukarya
Cytological features
Nucleus	No	No	Yes
Cytoskeleton	No	No	Yes
Organelles (mitochondria, chloroplasts, Golgi apparatus, endoplasmic reticulum)	No	No	Yes
Molecular features
DNA topology	Negatively supercoiled	Relaxed or positively supercoiled (in hyperthermophilic Archaea that contain reverse gyrase)	Negatively supercoiled
Promoter structure	Two conserved boxes at - 10 (TATAAT) and - 35 (TTGACA) from transcription start site	TATA box and/or initiator element	TATA box and/or initiator element
RNA polymerase	One type; relatively simple subunit composition; binds directly to promoter (can be footprinted)	One type; complex subunit structure (subunit pattern, genes, and serological properties similar to eukaryal RNA polymerase II); can be footprinted, but still requires basal transcription factors for promoter recognition [1, 2, 3,]	Three types; complex subunit compositions; cannot be footprinted; require basal transcription factors for promoter recognition/binding
Basal transcription factors	No	TBP , TFIIB, and TIIS homologs of eucaryal RNA polymerase II-associated factors described thus far	TBP, TAFs, TFIIA, TFIIB, TFIIE, TFIIF, TFIIH required for RNA polymerase II initiation; P-TEFb, TFIIS, TFIIF, elongin, and ELL required for elongation
Poly(A) tails in RNA	Short	Short (avg. 12 bases in length)	Long
Chromatin	No	?	Yes

Table adapted from Archaeal chromatin: Virtual or real? Jordanka Zlatanova Proc. Natl. Acad. Sci. USA, Vol. 94, pp. 12251-12254, November 1997

For further features and references see the series of minireviews on Archaea published in the June 27, 1997, issue of Cell, and refs. 5 and 27.

 Cell walls of Prokaryotes  Electron acceptors for respiration and methanogenesis in prokaryotes  Glycolysis in bacteria  Lithotrophic prokaryotes  Gene Regulation in E.coli  Second Messengers  Cell signaling