Restoration of flagellar biosynthesis by varied mutational events in Campylobacter jejuni

Department of Microbiology, The University of Texas Southwestern Medical Center, Dallas, TX, USA.
Molecular Microbiology (Impact Factor: 4.42). 09/2008; 70(2):519-36. DOI: 10.1111/j.1365-2958.2008.06428.x
Source: PubMed


Both a complex regulatory cascade involving the FlgSR two-component system and phase variation control expression of sigma(54)-dependent flagellar genes in Campylobacter jejuni. In this study, mutational mechanisms influencing production of the FlgS histidine kinase were discovered. Random non-motile, non-flagellated flgS variants were impaired for growth in the chick intestinal tract. Spontaneous revertants restored for flagellar biosynthesis, gene expression, and motility identified by in vivo and in vitro studies had undergone diverse intragenic and extragenic mutational events relative to flgS. Restorative intragenic events included true phase variation, second-site intragenic reversion, and insertion and deletion of short DNA segments within flgS. In vivo-isolated motile revertants possessed an identical, single extragenic mutation to create a partially constitutively active FlgR protein in the absence of FlgS. Considering that FlgR production is also influenced by phase variation, these new findings suggest that the FlgSR two-component system is unique in that each protein is controlled by phase variation and phosphorylation. In addition, this study highlights the mutational activities of C. jejuni and suggests that the bacterium may possess a repertoire of mutational mechanisms to overcome genetic lesions that impair production of virulence and colonization determinants while lacking a normal mismatch repair system.

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Available from: David Hendrixson, Aug 26, 2014
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    • "Alternatively, pseudorevertants can arise in which nucleotides are removed or added close to the original mutated homopolymeric nucleotide tract to restore the correct reading frame but which result in changes in the amino acid sequence of the protein [113]. flgS is also regulated by phase variation in C. jejuni, providing multiple levels of phase-variable control for the RpoN regulon [114, 115]. Similar mechanisms of phase variation also exist for flhA in C. coli [116] and fliP in H. pylori [117] which leads to the formation of truncated proteins that prevent flagellar biogenesis. "
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    ABSTRACT: 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 σ (54) (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.
    01/2014; 2014(12):681754. DOI:10.1155/2014/681754
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    • "Flagellar expression is subject to phase variation and contributes to the unstable motile phenotype in Campylobacter. Phase variation between motile and non‐motile phenotypes occurs frequently in vitro and in vivo (Caldwell et al., 1985; Karlyshev et al., 2002; Hendrixson, 2006; 2008), and is mediated by slipped‐strand mispairing primarily in homopolymeric or occasionally heteropolymeric tracts, resulting in frameshift mutations in the genes associated with flagellar biosynthesis and regulation (flhA, flgS, flgR and maf) (Park et al., 2000; Karlyshev et al., 2002; Hendrixson, 2006; 2008). The high‐frequency phase variation was attributed to the A/T‐rich genetic content of the C. jejuni chromosome and the absence of an intact mismatch repair system (Hendrixson, 2006). "
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    ABSTRACT: Campylobacter jejuni is a major foodborne pathogen of animal origin and a leading cause of bacterial gastroenteritis in humans. During the past decade, especially since the publication of the first C. jejuni genome sequence, major advances have been made in understanding the pathobiology and physiology of this organism. It is apparent that C. jejuni utilizes sophisticated mechanisms for effective colonization of the intestinal tracts in various animal species. Although Campylobacter is fragile in the environment and requires fastidious growth conditions, it exhibits great flexibility in the adaptation to various habitats including the gastrointestinal tract. This high adaptability is attributable to its genetically, metabolically and phenotypically diverse population structure and its ability to change in response to various challenges. Unlike other enteric pathogens, such as Escherichia coli and Salmonella, Campylobacter is unable to utilize exogenous glucose and mainly depends on the catabolism of amino acids as a carbon source. Campylobacter proves highly mutable in response to antibiotic treatments and possesses eukaryote-like dual protein glycosylation systems, which modify flagella and other surface proteins with specific sugar structures. In this review we will summarize the distinct biological traits of Campylobacter and discuss the potential biotechnological approaches that can be developed to control this enteric pathogen.
    Microbial Biotechnology 05/2010; 3(3):242-58. DOI:10.1111/j.1751-7915.2009.00118.x · 3.21 Impact Factor
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    • "In support of this idea, others have observed that mutations in specific contingency genes affect the ability of C. jejuni to invade epithelial cells (in vitro) (Guerry et al., 2002), the antigenicity of specific cell-surface molecules (glycoproteins) associated with molecular mimicry both in vitro and in experimental human infection (Bernatchez et al., 2007; Linton et al., 2000; Guerry et al., 2002; Prendergast et al., 2004), and the colonization of chickens (Ashgar et al., 2007; Hendrixson, 2008). Several groups have also demonstrated that the C. jejuni genotype can affect colonization of the GI tract of poultry (Ahmed et al., 2002; Hook et al., 2005; Coward et al., 2008; Ridley et al., 2008) and that passage through poultry can affect both the genotype and colonization of poultry (Cawthraw et al., 1996; Wassenaar et al., 1998; Ringoir & Korolik, 2003; Jones et al., 2004; Kakuda & DiRita, 2006). "
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    ABSTRACT: Previous studies have demonstrated that Campylobacter jejuni, the leading causative agent of bacterial food-borne disease in the USA, exhibits high-frequency genetic variation that is associated with changes in cell-surface antigens and ability to colonize chickens. To expand our understanding of the role of genetic diversity in the disease process, we analysed the ability of three C. jejuni human disease isolates (strains 11168, 33292 and 81-176) and genetically marked derivatives to colonize Ross 308 broilers and C57BL/6J IL10-deficient mice. C. jejuni colonized broilers at much higher efficiency (all three strains, 23 of 24 broilers) than mice (11168 only, 8 of 24 mice). C. jejuni 11168 genetically marked strains colonized mice at very low efficiency (2 of 42 mice); however, C. jejuni reisolated from mice colonized both mice and broilers at high efficiency, suggesting that this pathogen can adapt genetically in the mouse. We compared the genome composition in the three wild-type C. jejuni strains and derivatives by microarray DNA/DNA hybridization analysis; the data demonstrated a high degree of genetic diversity in three gene clusters associated with synthesis and modification of the cell-surface structures capsule, flagella and lipo-oligosaccharide. Finally, we analysed the frequency of mutation in homopolymeric tracts associated with the contingency genes wlaN (GC tract) and flgR (AT tracts) in culture and after passage through broilers and mice. C. jejuni adapted genetically in culture at high frequency and the degree of genetic diversity was increased by passage through broilers but was nearly eliminated in the gastrointestinal tract of mice. The data suggest that the broiler gastrointestinal tract provides an environment which promotes outgrowth and genetic variation in C. jejuni; the enhancement of genetic diversity at this location may contribute to its importance as a human disease reservoir.
    Microbiology 04/2010; 156(Pt 7):2046-57. DOI:10.1099/mic.0.035717-0 · 2.56 Impact Factor
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