**Horizontal Gene Transfer and the Diversity of** *Escherichia coli*

Maryam Javadi, Saeid Bouzari and Mana Oloomi

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.68307

### **Abstract**

Escherichia coli (E. coli) strains are normal flora of human gastrointestinal tract. The evo‐ lution encoded by horizontally-transferred genetic (HGT) elements has been perceived in several species. E. coli strains have acquired virulence potential factors by attainment of particular loci through HGT, transposons or phages. The heterogeneous nature of these strains is because of HGT through mobile genetic elements. These genetic exchanges that occur in bacteria provide the genetic diversity.

A diverse enterobacterial species of E. coli is classified into (i) commensal nonpathogenic, (ii) intestinal and (iii) extraintestinal pathogenic strains. This is related to the presence or absence of regions which are associated with certain pathotypes. The genetic information belongs to the flexible E. coli genome and it has been horizontally acquired by plasmids, bacteriophages and genomic islands. The rapid evolution of E. coli variants results from the genomic regions, contribute to frequently rearrangements, excision and transfer as well as acquisition of additional genome thus resulting to the creation of new (pathogenic) variants.

HGT is a key step in the evolution of bacterial pathogens. This study is focused on determining the common virulence factors as a signature at the genetic level to use for classification, diversity and evolution of E. coli.

**Keywords:** *Escherichia coli* (*E. coli*), horizontal gene transfer (HGT), pathogenicity islands (PAIs), evolution, bacteriophages

© 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
