Whole-genome analysis of pathogen evolution

Abstract

Abstract Whole-genome sequences for many bacterial species have initiated a new era of analysis. Horizontal gene exchange may be the dominant mechanism of adaptation. Bacterial chromosomes can be divided into core and accessory genes. Core genes are more likely to be involved in central processes such as transcription and translation, and are less likely to be horizontally exchanged. Accessory genes are more likely to be involved in adaptation and pathogenicity, and to have been horizontally acquired. Bacteria can evolve very rapidly in new niches, sometimes via genome degradation as well as gene acquisition. Many pathogenic bacteria have specialized mechanisms for generating diversity in otherwise clonal populations that are used to adapt to rapidly or randomly changing environments. Bacteria evolve under many selective pressures, not just the requirements of pathogenicity, including via ‘arms-races’ with their own parasites.