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Category: Bacterial Pathogenesis
Motility, Chemotaxis, and Flagella, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555818005/9781555812133_Chap21-1.gif /docserver/preview/fulltext/10.1128/9781555818005/9781555812133_Chap21-2.gifAbstract:
For many pathogenic bacteria, flagellum-dependent motility and chemotaxis are crucial factors in the process of colonization of the host organism and establishment of a successful infection. Structural components of the flagellum as well as secretory and regulatory proteins involved in the synthesis of the flagellar apparatus and the control of chemotaxis have been analyzed in recent years, and knowledge regarding the mechanisms of Helicobacter pylori motility is rapidly increasing. The chapter summarizes the available experimental and genomic data on flagellar function and provides an overview of the current knowledge of this field. Transcription of s54-dependent genes depends on upstream enhancer-like sequences, which are bound by a class of transactivating proteins usually referred to as the NtrC (NR-1) family. Characterized loci include the fliI-fliQ operon coding for two flagellar export proteins and a stress-responsive operon containing the gene encoding the chemotaxis regulator CheY. Both of these operons have been shown to be regulated by a σ80-dependent transcription, and sequence analysis of the H. pylori genome suggests that the expression of the other flagellar biosynthetic, basal-body, and chemotaxis genes also is regulated by the same sigma factor. The regulation of chemotaxis has been extensively studied in the model organisms Escherichia coli and Salmonella enterica serovar Typhimurium. In these bacteria, sensing of chemoattractants or -repellents is mediated by methyl-accepting chemotaxis proteins (MCP), which possess a periplasmic ligand interaction domain and a large cytoplasmic signaling and adaptation domain.
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Flagellar and chemotaxis proteins and their putative locations and interactions. The protein components of the major elements of the flagellum, the external filament, the hook, the basal body, and the motor-switch complex are shown. The external flagellar proteins that form the rod, hook, and filament are secreted by a specific export apparatus forming at the cytoplasmic side of the MS ring. The proton gradient at the cytoplasmic membrane drives a proton flow that energizes flagellar motor rotation. The direction of rotation is determined by the interaction of FliM in the motor-switch complex with the chemotaxis regulator CheY, whose activity is regulated by the other components of the chemotaxis system. Symbols: H+, protons; P, phosphate; CH3, methyl group.
Flagellar and chemotaxis proteins and their putative locations and interactions. The protein components of the major elements of the flagellum, the external filament, the hook, the basal body, and the motor-switch complex are shown. The external flagellar proteins that form the rod, hook, and filament are secreted by a specific export apparatus forming at the cytoplasmic side of the MS ring. The proton gradient at the cytoplasmic membrane drives a proton flow that energizes flagellar motor rotation. The direction of rotation is determined by the interaction of FliM in the motor-switch complex with the chemotaxis regulator CheY, whose activity is regulated by the other components of the chemotaxis system. Symbols: H+, protons; P, phosphate; CH3, methyl group.
Comparison of flagellar regulatory hierarchies in S. enterica serovar Typhimurium (A), C. crescentus (B), and H. pylori (C). Dependence of transcription on the specified sigma factors is indicated. Classes of flagellar genes are indicated by roman numbers. H. pylori genes and operons whose promoters have been deduced on the basis of nucleotide sequence analysis are enclosed by gray boxes. Symbols:↱ promoter, ↓activation, ⊥ repression.
Comparison of flagellar regulatory hierarchies in S. enterica serovar Typhimurium (A), C. crescentus (B), and H. pylori (C). Dependence of transcription on the specified sigma factors is indicated. Classes of flagellar genes are indicated by roman numbers. H. pylori genes and operons whose promoters have been deduced on the basis of nucleotide sequence analysis are enclosed by gray boxes. Symbols:↱ promoter, ↓activation, ⊥ repression.
Bacterial motility assay. The indicated strains were stab-inoculated into semisolid (0.3%) agar plates and incubated at 37°C for 3 days.
Bacterial motility assay. The indicated strains were stab-inoculated into semisolid (0.3%) agar plates and incubated at 37°C for 3 days.
Flagellar genes identified in the two published genome sequences a
Flagellar genes identified in the two published genome sequences a
Putative flagellar genes and operons and associated promoter sequences
Putative flagellar genes and operons and associated promoter sequences