50 Million Years of Genomic Stasis in Endosymbiotic Bacteria

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Science  28 Jun 2002:
Vol. 296, Issue 5577, pp. 2376-2379
DOI: 10.1126/science.1071278

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Comparison of two fully sequenced genomes ofBuchnera aphidicola, the obligate endosymbionts of aphids, reveals the most extreme genome stability to date: no chromosome rearrangements or gene acquisitions have occurred in the past 50 to 70 million years, despite substantial sequence evolution and the inactivation and loss of individual genes. In contrast, the genomes of their closest free-living relatives, Escherichia coli and Salmonella spp., are more than 2000-fold more labile in content and gene order. The genomic stasis of B. aphidicola, likely attributable to the loss of phages, repeated sequences, and recA, indicates thatB. aphidicola is no longer a source of ecological innovation for its hosts.

  • * These authors contributed equally to this work.

  • To whom correspondence should be addressed. E-mail: Siv.Andersson{at}

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