Microbial genomes

Abstract

With more than 200 bacterial and archaeal genomes completely sequenced, and more than 500 genomes at various stages of completion, we begin to appreciate the enormous diversity of prokaryotic genomes in terms of chromosomal structure, gene content and organization, and the abundance and fluidity of accessory and mobile genetic elements. The genome of a bacterial species is composed of conserved core genes and variable accessory genes. Mobile genetic elements, such as plasmids, transposons, insertion sequences, integrons, prophages, genomic islands, and pathogenicity islands, are part of the accessory genes, which can have a significant influence on the phenotype and biology of the organism. These mobile elements facilitate interspecies and intraspecies genetic exchange. They play an important role in the pathogenicity of bacteria, and are a major contributor to species diversity. Further genomic analysis will likely uncover more interesting genetic elements like small (noncoding) RNA genes that can play a significant role in gene regulation. © 2006 Humana Press Inc.