An Introduction to Microbial Genomic Islands for Evolutionary Adaptation and Pathogenicity

Abstract

Genomic islands (GEIs) play a vital role in the bacteria’s evolutionary adaptation and pathogenicity. GEIs are the unusual region located in the bacterial genome acquired through horizontal gene transfer (HGT). HGT is achieved through various ways, such as conjugation, transformation, and transduction. General features of GEIs are different G + C content as compared to other parts of the genome (core genome), size about 10–200 kb, association with tRNA-encoding genes, mostly flanked by repeat structures and may carry other accessory elements such as insertion sequence (IS) elements, plasmids, bacteriophages, and other mobile elements. GEIs are present in both pathogenic and non-pathogenic bacteria. Therefore, based on the composition, characteristics, and functions of GEIs, it has further divided into various islands such as pathogenicity, resistance, fitness and metabolic or symbiosis islands in pathogenic, environmental, commensal, and symbiotic bacteria. This chapter briefly highlights the GEIs and their role in the bacteria’s evolutionary adaptation and pathogenicity. In addition, the role of GEIs in pangenome is also discussed.