Taking the Long View

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Science  08 Aug 2008:
Vol. 321, Issue 5890, pp. 747
DOI: 10.1126/science.321.5890.747b

It can be difficult to establish the phylogeny of microorganisms because they are composed of genes that have moved vertically (via inheritance) or horizontally (via lateral transfer mechanisms such as conjugation) or both. Dagan et al. have applied a network analysis approach to estimate the cumulative impact of lateral gene transfer in the genomes of 181 fully sequenced prokaryotes. By examining the presence or absence of all genes and by tracing the evolutionary history of these genes on the basis of genome size, they were able to calculate the rate of lateral gene transfer and have concluded that approximately 80% of the genes in each genome appear to have been involved in lateral transfer at some point in their history. Hence, well-defined phylogenetic trees, which describe genetic relationships accurately on short-term evolutionary time scales, become rather less clearly delineated when looked at over very long time periods. — LMZ

Proc. Natl. Acad. Sci. U.S.A. 105, 10039 (2008).

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