A Putatively Phase Variable Gene (
 dca
 ) Required for Natural Competence in
 Neisseria gonorrhoeae
 but Not
 Neisseria meningitidis
 Is Located within the Division Cell Wall (
 dcw
 ) Gene Cluster

Snyder, Lori; Saunders, N.; Shafer, William M.

doi:10.1128/jb.183.4.1233-1241.2001

Cited by 25 publications

(32 citation statements)

References 66 publications

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“…In addition, the lpxA mutant was not naturally competent for DNA transformation. Several components have been implicated as essential for natural transformation in Neisseria, among which are pili, PilT, PilC, ComL, ComP, ComE, and Dca (4,9,38,40,42,51,52). Although most of the studies of DNA transformation have been performed with N. gonorrhoeae, many of the gene products have counterparts in meningococci, with the exception of Dca, which has been found only in gonococcal strains.…”

Section: Discussionmentioning

confidence: 99%

Lipooligosaccharide-DeficientNeisseria meningitidisShows Altered Pilus-Associated Characteristics

2003

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Molecular interaction between host mucosal surfaces and outer membrane components of microbes is crucial in the infection process. The outer membrane of pathogenic Neisseria contains surface molecules such as pili, PilC, and Opa and a monolayer of lipooligosaccharide (LOS), all of which are involved in the interaction with host cells. Pili mediate the initial attachment to human epithelial cells, which is followed by tight contact between bacteria and the eucaryotic cells, leading to bacterial invasion. To further examine the basis for bacterium-host cell contact, we constructed an LOS-deficient Neisseria meningitidis serogroup C mutant. LOS deficiency was without exception accompanied by altered colony opacity and morphology, which most likely represented an "on" switch for Opa540 expression, and by reduced levels of the iron-regulated proteins FetA and FbpA. We show here that LOS is essential for pilus-associated adherence but dispensable for fiber formation and twitching motility. The absence of attachment to epithelial cells could not be attributed to altered levels of piliation or defects in the pilus adhesion phenotype. Further, LOS mutants do not invade host cells and have lost the natural competence for genetic transformation.The mucosal epithelial cell barrier is the first physical defense encountered by bacteria upon contact with the human host. Immediately upon adherence of bacteria, the epithelial cells initiate a nonspecific or innate immune response by production of proinflammatory factors. The inflammatory response to bacterial infections plays an important role in detection and elimination of invading microorganisms. Various components of the bacterial cell wall such as peptidoglycan, lipoteichoic acid, lipoproteins, and lipopolysaccharide (LPS) are capable of activating the proinflammatory reaction. For gram-negative bacteria, LPS is the dominant trigger of the systemic inflammatory response. Recently, Toll-like receptors (TLRs) have been implicated in host responses to bacterial pathogens. Specifically, TLR4 mediates LPS responses whereas TLR2 plays a broader role in the recognition of a variety of bacteria and bacterial antigens (41). The host inflammatory response in meningococcal sepsis is generally believed to be induced by lipooligosaccharide (LOS).LOS of Neisseria meningitidis (meningococcus) is an endotoxin that is structurally distinct from LPS of enteric gramnegative bacteria (21, 33). Unlike most enteric LPSs, meningococcal LOS lacks O-antigen and possesses relatively short polysaccharides, only two to five sugar residues, attached to the meningococcal LOS inner core. LOS is an amphipathic molecule that consists of a hydrophilic carbohydrate portion and a hydrophobic lipid A portion that anchors the LOS to the outer membrane. Endotoxic shock is mediated by the lipid A portion of LOS and is characterized by activation of macrophages and production of a diverse array of cytokines, including those that act as chemoattractants for other leukocytes. Meningococcal septic shock is a direct r...

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Section: Discussionmentioning

confidence: 99%

Lipooligosaccharide-DeficientNeisseria meningitidisShows Altered Pilus-Associated Characteristics

2003

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“…The pptA::kan allele carried on plasmid pLS3 (44) was introduced into the wt strain N400 and into GV1 [pilV(Fs) (a null allele of pilV with a frameshift mutation at the G Ϫ1 codon (65)], by transformation and selection for kanamycin-resistant transformants, to generate the pptA null mutants designated KS9 (pptA::kan) and KS10 [pilV(Fs) pptA::kan]. The strains carrying the pptA LS1 ::kan allele carried on plasmid pLS1 (44) have been previously described (1).…”

Section: Methodsmentioning

confidence: 99%

Genetic and Functional Analyses of PptA, a Phospho-Form Transferase Targeting Type IV Pili inNeisseria gonorrhoeae

Næssan

Egge-Jacobsen

Heiniger³

et al. 2008

J Bacteriol

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The PilE pilin subunit protein of Neisseria gonorrhoeae undergoes unique covalent modifications with phosphoethanolamine (PE) and phosphocholine (PC). The pilin phospho-form transferase A (PptA) protein, required for these modifications, shows sequence relatedness with and architectural similarities to lipopolysaccharide PE transferases. Here, we used regulated expression and mutagenesis as means to better define the relationships between PptA structure and function, as well as to probe the mechanisms by which other factors impact the system. We show here that pptA expression is coupled at the level of transcription to its distal gene, murF, in a division/cell wall gene operon and that PptA can act in a dose-dependent fashion in PilE phosphoform modification. Molecular modeling and site-directed mutagenesis provided the first direct evidence that PptA is a member of the alkaline phosphatase superfamily of metalloenzymes with similar metal-binding sites and conserved structural folds. Through phylogenetic analyses and sequence alignments, these conclusions were extended to include the lipopolysaccharide PE transferases, including members of the disparate Lpt6 subfamily, and the MdoB family of phosphoglycerol transferases. Each of these enzymes thus likely acts as a phospholipid head group transferase whose catalytic mechanism involves a trans-esterification step generating a protein-phospho-form ester intermediate. Coexpression of PptA with PilE in Pseudomonas aeruginosa resulted in high levels of PE modification but was not sufficient for PC modification. This and other findings show that PptA-associated PC modification is governed by as-yet-undefined ancillary factors unique to N. gonorrhoeae.

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“…A further gene present in the MC58 genome sequence with homology to lpt-3, NMB0415, had no identifiable role in N. meningitidis LPS synthesis. NMB0415 had previously been studied in an investigation of murein sacculus formation in neisseria and was inferred to play some role in natural competence in Neisseria gonorrhoeae, but the precise role was not clear (22).…”

Section: Structural Characterization Of Lipid a Regions Of O-deacylatmentioning

confidence: 99%

Phosphorylation of the Lipid A Region of Meningococcal Lipopolysaccharide: Identification of a Family of Transferases That Add Phosphoethanolamine to Lipopolysaccharide

et al. 2003

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A gene, NMB1638, with homology to the recently characterized gene encoding a phosphoethanolamine transferase, lpt-3, has been identified from the Neisseria meningitidis genome sequence and was found to be present in all meningococcal strains examined. Homology comparison with other database sequences would suggest that NMB1638 and lpt-3 represent genes coding for members of a family of proteins of related function identified in a wide range of gram-negative species of bacteria. When grown and isolated under appropriate conditions, N. meningitidis elaborated lipopolysaccharide (LPS) containing a lipid A that was characteristically phosphorylated with multiple phosphate and phosphoethanolamine residues. In all meningococcal strains examined, each lipid A species contained the basal diphosphorylated species, wherein a phosphate group is attached to each glucosamine residue. Also elaborated within the population of LPS molecules are a variety of "phosphoforms" that contain either an additional phosphate residue, an additional phosphoethanolamine residue, additional phosphate and phosphoethanolamine residues, or an additional phosphate and two phosphoethanolamine residues in the lipid A. Mass spectroscopic analyses of LPS from three strains in which NMB1638 had been inactivated by a specific mutation indicated that there were no phosphoethanolamine residues included in the lipid A region of the LPS and that there was no further phosphorylation of lipid A beyond one additional phosphate species. We propose that NMB1638 encodes a phosphoethanolamine transferase specific for lipid A and propose naming the gene "lptA," for "LPS phosphoethenolamine transferase for lipid A."Lipopolysaccharide (LPS) is found in all gram-negative bacteria and is usually composed of three regions: lipid A, core oligosaccharide (OS), and a polysaccharide molecule often referred to as the "O-antigen." LPS from Neisseria meningitidis lacks the polysaccharide and is sometimes referred to as "lipooligosaccharide" (LOS) to reflect this. The core OS unit of N. meningitidis LPS comprises an inner core diheptose-N-acetylglucosamine backbone, wherein the two L-glycero-D-mannoheptose (Hep) residues can provide a point of attachment for outer core OS residues (8). Meningococcal LPS has been classified into 12 distinct LPS immunotypes (L1 to L12), originally defined by monoclonal antibody (MAb) reactivities (21) but further defined by structural analyses (4,5,7,9,14,16,26). The structural basis of the immunotyping scheme is primarily governed by the location of a phosphoethanolamine (PEtn) moiety on the distal heptose residue (HepII) at either the 3-or 6-position or absent, but is also dictated by the length and nature of OS extension from the proximal heptose residue (HepI) and the presence or absence of a glucose at HepII (17 [ Fig. 1]). The lipid A region of the LPS is responsible for much of the toxicity of the LPS molecule, and LPS is indeed sometimes referred to as "endotoxin." The lipid A region consists of a disaccharide of pyranosyl glucosamine r...

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A Putatively Phase Variable Gene ( dca ) Required for Natural Competence in Neisseria gonorrhoeae but Not Neisseria meningitidis Is Located within the Division Cell Wall ( dcw ) Gene Cluster

Cited by 25 publications

References 66 publications

Lipooligosaccharide-DeficientNeisseria meningitidisShows Altered Pilus-Associated Characteristics

Lipooligosaccharide-DeficientNeisseria meningitidisShows Altered Pilus-Associated Characteristics

Genetic and Functional Analyses of PptA, a Phospho-Form Transferase Targeting Type IV Pili inNeisseria gonorrhoeae

Phosphorylation of the Lipid A Region of Meningococcal Lipopolysaccharide: Identification of a Family of Transferases That Add Phosphoethanolamine to Lipopolysaccharide

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