Bacteria and Archaea

Researchers recently discovered that many prokaryotes once classified as bacteria are actually more closely related to eukaryotes and belong in a domain of their own. As a result, prokaryotes are now classified in two domains: Bacteria and Archaea. Many bacterial and archaeal genomes have now been sequenced. When compared with each other and with the genomes of eukaryotes, these genome sequences strongly support the three-domain view of life. Some genes of archaea are similar to bacterial genes, others are eukaryotic genes, and still others seem to be unique to archaea. Differences between the rRNA sequences provided the first clues of a deep division among prokaryotes. Other differences in the cellular machinery for gene expression include differences in RNA polymerases and in the presence of introns within genes. The cell walls and membranes of bacteria and archaea are also distinctive. Bacterial cell walls contain peptidoglycan, while archaea do not. Furthermore, the lipids forming the backbone of plasma membranes between the two domains. Intriguingly, archaea have at least as much in common with eukaryotes as they do with bacteria. -Biology book page 325

 

 

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