Regulation of Flagellar Gene Expression and Assembly

Abstract

Campylobacters produce proteins required for motility that are absent in other well studied motile bacteria, and have portions of conserved pathways mixed with unique mechanisms of promoting flagellar gene regulation, biosynthesis, and motility. Chemotaxis is an essential property of flagellar motility that influences the movement of bacteria toward appropriate environmental and host niches that support ideal bacterial growth and away from components that are less beneficial for growth or harmful to the organism. Although much information regarding flagellar motility has been gleaned by analyzing predictions from genomic sequences, the field of flagellar motility in campylobacters was moved forward by the development of new genetic tools and strategies for studying these bacteria. Seminal works for understanding regulatory pathways for flagellar gene expression and assembly of proteins into a flagellum largely focused on those of Salmonella species followed by Vibrio and Pseudomonas species. Early studies focusing on antigens of Campylobacter jejuni that are recognized by convalescent human antisera after infection revealed that the major flagellin FlaA is the foremost immunodominant antigen. Thus, much early work regarding flagellar motility in campylobacters largely centered on the genetic organization and expression of the flagellin genes of C. jejuni and C. coli. Flagellar motility in campylobacters is also affected by phase variation. Much progress has been made in the last decade in identifying proteins of campylobacters required for flagellar motility and understanding the roles of these proteins in flagellar gene regulation, biosynthesis of the organelle, and chemotaxis.