Article

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: 5.03). 09/2008; 70(2):519-36. DOI: 10.1111/j.1365-2958.2008.06428.x
Source: PubMed

ABSTRACT 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.

Download full-text

Full-text

Available from: David Hendrixson, Aug 26, 2014
0 Followers
 · 
75 Views
  • Source
    • "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). "
    [Show abstract] [Hide abstract]
    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 · 2.84 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Activation of sigma(54)-dependent gene expression essential for formation of flagella in Campylobacter jejuni requires the components of the inner membrane-localized flagellar export apparatus and the FlgSR two-component regulatory system. In this study, we characterized the FlgS sensor kinase and how activation of the protein is linked to the flagellar export apparatus. We found that FlgS is localized to the C. jejuni cytoplasm and that His141 of FlgS is essential for autophosphorylation, phosphorelay to the cognate FlgR response regulator, motility, and expression of sigma(54)-dependent flagellar genes. Mutants with incomplete flagellar export apparatuses produced wild-type levels of FlgS and FlgR, but they were defective for signaling through the FlgSR system. By using genetic approaches, we found that FlgSR activity is linked to and downstream of the flagellar export apparatus in a regulatory cascade that terminates in expression of sigma(54)-dependent flagellar genes. By analyzing defined flhB and fliI mutants of C. jejuni that form flagellar export apparatuses that are secretion incompetent, we determined that formation of the apparatus is required to contribute to the signal sensed by FlgS to terminate in activation of expression of sigma(54)-dependent flagellar genes. Considering that the flagellar export apparatuses of Escherichia coli and Salmonella species influence sigma(28)-dependent flagellar gene expression, our work expands the signaling activity of the apparatuses to include sigma(54)-dependent pathways of C. jejuni and possibly other motile bacteria. This study indicates that these apparatuses have broader functions beyond flagellar protein secretion, including activation of essential two-component regulatory systems required for expression of sigma(54)-dependent flagellar genes.
    Journal of bacteriology 03/2009; 191(8):2656-67. DOI:10.1128/JB.01689-08 · 2.69 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Traditionally, glycoproteins have been considered the exclusive property of eukaryotes and archaea, but it is now evident that glycoproteins are found in all domains of life. In recent years N-linked glycosylation among some epsilon-proteobacteria has emerged as a new and exciting research area and represents a useful model to understand this complex process in simple, genetically tractable bacteria. Above all, the transfer of N-linked glycosylation systems to the work-horse bacterium, Escherichia coli, has enabled, for the first time, the production of recombinant glycoproteins. This has potentially provided the option for tailor-made glycoproteins and has opened up the field of glycoengineering, particularly with respect to the development of glycoconjugate vaccines.
    Future Microbiology 06/2009; 4(4):401-12. DOI:10.2217/fmb.09.10 · 3.82 Impact Factor
Show more