An Archaeal Signature

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Science  31 Mar 2000:
Vol. 287, Issue 5462, pp. 2377
DOI: 10.1126/science.287.5462.2377e

Genome sequencing continues to provide tantalizing new perspectives on the phylogenetic relationships between organisms. The great advantage of genome sequencing over other methods is that it removes the subjectivity of reliance on particular phenotypic characters or molecular sequences when trying to classify organisms. The disadvantage, of course, is that it is much more expensive and time-consuming, but judicious genomic sampling of the Tree of Life is beginning to provide hard data about the true differences and relationships between higher-order taxa such as kingdoms and phyla.

Graham et al. use four completed archaean genome sequences to define a genomic ‘signature’ for the Archaea, formerly grouped with the Bacteria as ‘prokaryotes.’ They identify 351 clusters of proteins, or some 15% of the total number of archaean proteins, that are unique to the Archaea. This result sets the stage for an objective assessment of the relationship of the Archaea to other groups, notably Bacteria and Eukarya, and promises much for the understanding of the evolution of genes and proteins.—AMS

Proc. Natl. Acad. Sci. U.S.A., in press.


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