Dataset Information

Implications of phase variation of a gene (pgtA) encoding a pilin galactosyl transferase in gonococcal pathogenesis.

ABSTRACT: The pilin glycoprotein (PilE) is the main building block of the pilus of Neisseria gonorrhoeae (gonococcus [GC]). GC pilin is known to carry a disaccharide O-glycan, which has an alphaGal attached to the O-linked GlcNAc by a 1-3 glycosidic bond. In this report, we describe the cloning and characterization of the GC gene, pilus glycosyl transferase A (pgtA), which encodes the galactosyl transferase that catalyzes the synthesis of this Gal-GlcNAc bond of pilin glycan. A homopolymeric tract of Gs (poly-G) is present in the pgtA gene of many GC strains, and this pgtA with poly-G can undergo phase variation (Pv). However, in many other GC, pgtA lacks the poly-G and is expressed constitutively without Pv. Furthermore, by screening a large number of clinical isolates, a significant correlation was observed between the presence of poly-G in pgtA and the dissemination of GC infection. Poly-G was found in pgtA in all (24 out of 24) of the isolates from patients with disseminated gonococcal infection (DGI). In contrast, for the vast majority (20 out of 28) of GC isolated from uncomplicated gonorrhea (UG) patients, pgtA lacked the poly-G. These results indicate that Pv of pgtA is likely to be involved in the conversion of UG to DGI.

SUBMITTER: Banerjee A

PROVIDER: S-EPMC2193922 | biostudies-literature | 2002 Jul

REPOSITORIES: biostudies-literature

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Implications of phase variation of a gene (pgtA) encoding a pilin galactosyl transferase in gonococcal pathogenesis.

Banerjee Asesh A Wang Rong R Supernavage Sherry L SL Ghosh Salil K SK Parker James J Ganesh Nisha F NF Wang Peng G PG Gulati Sunita S Rice Peter A PA

The Journal of experimental medicine 20020701 2

The pilin glycoprotein (PilE) is the main building block of the pilus of Neisseria gonorrhoeae (gonococcus [GC]). GC pilin is known to carry a disaccharide O-glycan, which has an alphaGal attached to the O-linked GlcNAc by a 1-3 glycosidic bond. In this report, we describe the cloning and characterization of the GC gene, pilus glycosyl transferase A (pgtA), which encodes the galactosyl transferase that catalyzes the synthesis of this Gal-GlcNAc bond of pilin glycan. A homopolymeric tract of Gs ( ...[more]

PMID: 12119340

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Project description:UnlabelledExtracellular DNA is an important structural component of many bacterial biofilms. It is unknown, however, to which extent external DNA is used to transfer genes by means of transformation. Here, we quantified the acquisition of multidrug resistance and visualized its spread under selective and nonselective conditions in biofilms formed by Neisseria gonorrhoeae. The density and architecture of the biofilms were controlled by microstructuring the substratum for bacterial adhesion. Horizontal transfer of antibiotic resistance genes between cocultured strains, each carrying a single resistance, occurred efficiently in early biofilms. The efficiency of gene transfer was higher in early biofilms than between planktonic cells. It was strongly reduced after 24 h and independent of biofilm density. Pilin antigenic variation caused a high fraction of nonpiliated bacteria but was not responsible for the reduced gene transfer at later stages. When selective pressure was applied to dense biofilms using antibiotics at their MIC, the double-resistant bacteria did not show a significant growth advantage. In loosely connected biofilms, the spreading of double-resistant clones was prominent. We conclude that multidrug resistance readily develops in early gonococcal biofilms through horizontal gene transfer. However, selection and spreading of the multiresistant clones are heavily suppressed in dense biofilms.ImportanceBiofilms are considered ideal reaction chambers for horizontal gene transfer and development of multidrug resistances. The rate at which genes are exchanged within biofilms is unknown. Here, we quantified the acquisition of double-drug resistance by gene transfer between gonococci with single resistances. At early biofilm stages, the transfer efficiency was higher than for planktonic cells but then decreased with biofilm age. The surface topography affected the architecture of the biofilm. While the efficiency of gene transfer was independent of the architecture, spreading of double-resistant bacteria under selective conditions was strongly enhanced in loose biofilms. We propose that while biofilms help generating multiresistant strains, selection takes place mostly after dispersal from the biofilm.

Project description:The obligate human pathogen Neisseria gonorrhoeae is the sole aetiologic agent of the sexually transmitted infection, gonorrhea. Required for gonococcal infection, Type IV pili (Tfp) mediate many functions including adherence, twitching motility, defense against neutrophil killing, and natural transformation. Critical for immune escape, the gonococcal Tfp undergoes antigenic variation, a recombination event at the pilE locus that varies the surface exposed residues of the major pilus subunit PilE (pilin) in the pilus fiber. This programmed recombination system has the potential to produce thousands of pilin variants and can produce strains with unproductive pilin molecules that are completely unable to form Tfp. Saturating mutagenesis of the 3' third of the pilE gene identified 68 unique single nucleotide mutations that each resulted in an underpiliated colony morphology. Notably, all isolates, including those with undetectable levels of pilin protein and no observable surface-exposed pili, retained an intermediate level of transformation competence not exhibited in ΔpilE strains. Site-directed, nonsense mutations revealed that only the first 38 amino acids of the mature pilin N-terminus (the N-terminal domain or Ntd) are required for transformation competence, and microscopy, ELISAs and pilus purification demonstrate that extended Tfp are not required for competence. Transformation in strains producing only the pilin Ntd has the same genetic determinants as wild-type transformation. The Ntd corresponds to the alternative product of S-pilin cleavage, a specific proteolysis unique to pathogenic Neisseria. Mutation of the S-pilin cleavage site demonstrated that S-pilin cleavage mediated release of the Ntd is required for competence when a strain produces unproductive pilin molecules that cannot assemble into a Tfp through mutation or antigenic variation. We conclude that S-pilin cleavage evolved as a mechanism to maintain competence in nonpiliated antigenic variants and suggest there are alternate forms of the Tfp assembly apparatus that mediate various functions including transformation.

Dataset Information

Implications of phase variation of a gene (pgtA) encoding a pilin galactosyl transferase in gonococcal pathogenesis.

Publications

Implications of phase variation of a gene (pgtA) encoding a pilin galactosyl transferase in gonococcal pathogenesis.

Similar Datasets

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