Genome plasticity in Enterobacteriaceae.

The comparative analysis of multiple representatives of the genomes of particular species are leading us away from a view of bacterial genomes as static, monolithic structures towards the view that they are relatively variable, fluid structures. This plasticity is mainly the result of the rearrangement of genes within the genome and the acquisition of novel genes by horizontal transfer systems, e. g. plasmids, bacteriophages, transposons or gene cassettes. These mechanisms often act in concert thus generating a complex genetic structure. Genomic variations are not a phenomenon at the DNA level alone, they influence the phenotype of a bacterium as well and can render a formerly harmless organism into a hazardous pathogen. This review deals not only with the mechanisms of genome rearrangements and the horizontal transfer of genes in Enterobacteriaceae but also points out that mobile genetic elements themselves are subjected to variation.