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CHAPTER 27: BACTERIA AND ARCHAEA
I.

27.1 Diversity and Evolution
A. Archaea
1. Prokaryotic cell structure
2. More closely related to Domain Eukarya than to Domain Bacteria
a) Have more complex RNA than bacteria
b) Membrane lipids feature ether linkages
(1) More stable under extreme environmental conditions
c) Archaea do not have peptidoglycan cell walls
(1) Have outer coverings made of protein instead
B. Bacteria
1. Prokaryotic cell structure
2. Membrane lipids are formed with ester linkages
3. Cell walls can contain peptidoglycan
C. Domain Archaea Was Ancestral to Domain Eukarya

Fig. 27.2 Bacteria and Archaea

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1. DNA with histone proteins (shared with Eukarya)
(1) Archaea and Eukarya share over 30 ribosomal proteins that are not present in bacteria
(2) Archaeal and Eukaryotic RNA polymerases are closely related
2. Ether-linked cell membranes
a) Ester bonds are in bacteria and eukaryotes
b) Ether bonds are unique to archaea
(1) Ether bonds are resistant to damage by heat and other extreme conditions
(a) Explains why extremophiles are able to exist
c) Archaea also use isoprene chains instead of fatty acid chains in making membranes 3. Extremophiles
a) Organisms that occur primarily in extreme habitats
4. Hypothermophiles
a) An organism that thrives in extremely hot environments
b) Methanopyrus
(1) Grows best at deep sea thermal vent sites
(a) Where the temperature is 98 degrees celsius

Both are Methanopyrus

(b) It actually can not grow when the temperature is less than 84 degrees celsius
(2) In the phylum Euryarchaeota
5. High temperatures and low pH
a) Sulfolobus
(1) From sulfur hot springs with a pH of 3 or lower
(2) In the phylum Crenarchaeota
6. Halophiles
a) Species able to grow in higher than usual salt concentrations

Sulfolobus

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b) Rhodopsin
(1) Retinal-binding proteins that provide light-dependent ion transport and sensory functions to