Bringing order to a complex molecular machine: The assembly of the bacterial flagella

Abstract

The bacterial flagellum is an example of elegance in molecular engineering. Flagella dependent motility is a widespread and evolutionarily ancient trait. Diverse bacterial species have evolved unique structural adaptations enabling them to migrate in their environmental niche. Variability exists in the number, location and configuration of flagella, and reflects unique adaptations of the microorganism. The most detailed analysis of flagellar morphogenesis and structure has focused on Escherichia coli and Salmonella enterica. The appendage assembles sequentially from the inner to the outer-most structures. Additionally the temporal order of gene expression correlates with the assembly order of encoded proteins into the final structure. The bacterial flagellar apparatus includes an essential basal body complex that comprises the export machinery required for assembly of the hook and flagellar filament. A review outlining the current understanding of the protein interactions that make up this remarkable structure will be presented, and the associated temporal genetic regulation will be briefly discussed.

Control of gene expression by type III secretory activity

“…The bacterial flagellum is assembled in a sequential manner involving more than 30 gene products and has been studied most extensively in Salmonella enterica serovar Typhimurium [3,[7][8][9]. Flagellar genes are generally divided into early, middle, and late (expressed from class I, II, and III promoters, respectively) based upon their temporal expression patterns.…”

“…One of those pathways, the type III secretion system (T3SS), can be divided into two major classes, flagellar and nonflagellar. The flagellar T3SS is associated with the MS ring of the basal body and is responsible for secreting the extracytoplasmic components of the flagellum [3]. The non-flagellar T3SS is associated with the bacterial injectisome, which translocates effector proteins into the cytoplasm of eukaryotic host cells to promote the pathogenic/symbiotic lifestyle of the microorganism [4,5].…”

The Essential Protein for Bacterial Flagella Formation FlgJ Functions as a β-N-Acetylglucosaminidase

“…4), which involves 20 different proteins. These proteins form a hetero-oligomeric structure comprised of three major substructures: a basal body that spans the cell wall, a connecting hook, and a thin helical filament that extends into the extracellular environment (5).…”

Characterizing the Rogues and Smooth Pairs of Cronobacter sakazakii Involved in Biofilm Formation and Long-Term Survival

“…Whether the different reactions affect the quantity of biofilm formation still needs further investigation. A bacterial flagellum is comprised of a basal body, a hook and a filament (Apel and Surette, 2008). PCR primers targeted flagella hook and filament structure genes showed only filament gene fliC was absent in strain 713S.…”