The genomic tree of living organisms based on a fractal model ✩

Accumulation of complete genome sequences of living organisms creates new possibilities to discuss the phylogenetic relationships at the genomic level. In the present Letter, a fractal model is proposed to simulate a kind of visual representation of complete genome. The estimated parameters in the fractal model is used to define the genetic distance between two organisms. Because we take into account all genome content including both coding and non-coding regions, the phylogenetic tree from such an analysis leads to alternate classification of genomes that is called a genomic tree. This method of phylogenetic analysis does not require sequence alignment of homologous genes and relies instead on our fractal analysis, so it can avoid artefacts associated with sequence alignment. The similarity in related organisms based on the fractal model of the complete genome is global. Our result from such an analysis of more than 50 genomes indicates that lateral gene transfer must have been very common in the early history of life and thus constitutes a major source of variations in a substantial proportion of prokaryotic genome.  2003 Elsevier B.V. All rights reserved.