Origin and Evolution of the Bacterial Flagellar System
from: Pili and Flagella: Current Research and Future Trends (Edited by: Ken Jarrell). Caister Academic Press, U.K. (2009)
Elucidating the origin and evolution of complex systems such as the bacterial flagellum is one of the major challenges of evolutionary studies. Taking advantages of whole genome sequences from hundreds of bacterial genomes, recent studies have shown that the bacterial flagellum evolved from a simple secretion system to a well-honed structure, and various evolutionary forces have contributed to the stepwise formation process, including gene duplication, horizontal gene transfer, and gene loss. Whereas structural genes arose before the divergence of major bacterial lineages, auxiliary and regulatory genes are recruited in a lineage-specific fashion. Although the physical structure of the flagellum is conserved across bacterial phyla, the composition, organization, and operon structure of flagellar genes are under constant modification. Additional genome sequences and better functional characterization of genetic components will help illustrate details of the evolutionary process in the future read more ...