Lateral gene transfer detected by comparing the genomes of Escherichia coli HS and Shigella dysenteriae Sd197.

摘要

Large scale genome rearrangement plays an important role in bacterial genome evolution and this arrangement can be attributed in part to lateral gene transfer. Lateral transfer of genes involves movement of genes between species. The classification of bacteria into discrete taxonomic units is considered to be obstructed by the potential for lateral gene transfer (LGT) among lineages at virtually all phylogenetic levels. In most bacterial genomes, large proportions of genes are introduced by lateral gene transfer, as indicated by their compositional features and/or phylogenetic distributions, and there is also clear evidence of LGT between very distantly related organisms. In this study homologous genes from two serologically related bacterial species, Escherichia coli HS and Shigella dysenteriae Sd197 were compared through genome alignment to detect genes suspected to be candidates of lateral gene transfer and the presence or absence of genes from each genome was catalogued after alignment. Absence of the gene in one of the two strains may indicate lateral transfer or gene loss. Lateral transfer candidate genes were studied further to determine other organisms with these genes in their genomes, and phylogenetic trees were constructed. The study showed that Escherichia coli HS and Shigella dysenteriae Sd197 have gone through genome evolution by the loss and gain of genes, it also showed possible lateral genes transfer between bacteria and distantly related organisms like fungi, viruses and even insects.