Archaea vs Bacteria

[RLM222]

What is need to differentiate an archaea from bacteria? What kind of tests or materials? How are they generally differentiated?

[stopherlogic]

Small subunit rRNA sequence analysis

[alextemplet]

Ribosomal RNA is the primary method of differentiation, but there's also differences in how they live. Archaea are mostly extremophiles. It's believed that archaea are actually the ancestors of eukaryotes, and not bacteria.

[MrMistery]

There are many differences between Archea and Bacteria.
The fact that the rRNA sequence of the Archean 16S is closer to the eukaryotic 18S than to Bacterial 16S is indeed the way they were classified, but there many more differences.
The way they live - this is tricky, as (if my memory serves me) not all Archea are extremophiles and some Bacteria are extremophiles also.
Some more important distinctions include:
-archea have a different kind of cell wall that lacks murein, and some lack a cell wall entirely
-archea have a very different plasma membrane that is not a bilayer, but is instead composed of long branched carbon chains that have glycerol attached at both ends.
-glycerol in archean cell membranes is in a different stereoisomer than in every other cell
-archea have 3 RNA polymerases like eukaryotes, bacteria have only one
-there are numerous cases of introns in archea, whereas in bacteria these are very rare
-the two react to various antibiotics differently (don't remember which - look it up if you wish)

And to clear up something Alex said. Archea are not the ancestors of anything. It is true that it is believed that the ancestor of eukaryotes was an archean-like cell (the last common ancestor of archea and eukaryotes lived more recently than the last common ancestor of archea and bacteria), but it is very important to keep in mind that "Archea" refers to contemporary cells only.

[rexacrouch]

This paper explains the difference between Archaea and Bacteria fairly well:

http://www.scribd.com/doc/13063682/A-Br ... -Industry-

[canalon]

Just a note MrMistery,
Not all Archae have a single layered membrane. Some do some don't, but the link between the glycerol and the fatty acid is always an ether bond, unlike bacteria.
And yes there are a lot of bacterila extremophiles, and a lot of archae that are not extremophile, so this is not a good way to differentiate them.

[MrMistery]

ups yeah, I was a bit careless there. Could thing you caught that, we don't want to be misinforming people