%0 Journal Article
%T Themes and Variations: Regulation of RpoN-Dependent Flagellar Genes across Diverse Bacterial Species
%A Jennifer Tsang
%A Timothy R. Hoover
%J Scientifica
%D 2014
%I Hindawi Publishing Corporation
%R 10.1155/2014/681754
%X Flagellar biogenesis in bacteria is a complex process in which the transcription of dozens of structural and regulatory genes is coordinated with the assembly of the flagellum. Although the overall process of flagellar biogenesis is conserved among bacteria, the mechanisms used to regulate flagellar gene expression vary greatly among different bacterial species. Many bacteria use the alternative sigma factor ¦Ò54 (also known as RpoN) to transcribe specific sets of flagellar genes. These bacteria include members of the Epsilonproteobacteria (e.g., Helicobacter pylori and Campylobacter jejuni), Gammaproteobacteria (e.g., Vibrio and Pseudomonas species), and Alphaproteobacteria (e.g., Caulobacter crescentus). This review characterizes the flagellar transcriptional hierarchies in these bacteria and examines what is known about how flagellar gene regulation is linked with other processes including growth phase, quorum sensing, and host colonization. 1. Introduction The flagellum is an exquisitely complex nanomachine that is the primary means for motility in many bacteria. Given that motility plays a vital role in important microbial processes such as chemotaxis, host colonization, and biofilm formation, understanding how bacteria regulate flagellar biogenesis is critical for developing new strategies for the control of harmful microbes and manipulation of useful ones. Flagellar biogenesis is a highly ordered process that involves the coordinated regulation of dozens of structural and regulatory genes with the assembly of the flagellum. As expected for choreographing such an intricate process, flagellar biogenesis involves some of the most sophisticated regulatory mechanisms found in microbiology. Although the structure of the flagellum differs slightly between Gram-negative type and Gram-positive type bacteria, in all cases the bacterial flagellum is comprised of three main parts: the basal body, hook, and filament [1]. Components of the basal body are located within or are closely associated with the cell envelope. The basal body consists of several distinct structures, including the C ring, a type III secretion system known as the flagellar protein export apparatus, the flagellar motor, the rod, and rings that anchor the flagellum to the membrane (Figure 1(a)). Both Gram-negative and Gram-positive type bacteria possess MS and P rings, located in the inner membrane and peptidoglycan layer, respectively. Gram-negative type bacteria possess another ring known as the L ring located in the outer membrane. These rings provide support for the rod as it goes
%U http://www.hindawi.com/journals/scientifica/2014/681754/