Dataset Information

Polymorphisms in pilin glycosylation Locus of Neisseria meningitidis expressing class II pili.

ABSTRACT: We have located a locus, pgl, in Neisseria meningitidis strain NMB required for the glycosylation of class II pili. Between five and eight open reading frames (ORFs) (pglF, pglB, pglC, pglB2, orf2, orf3, orf8, and avtA) were present in the pgl clusters of different meningococcal isolates. The Class I pilus-expressing strains Neisseria gonorrhoeae MS11 and N. meningitidis MC58 each contain a pgl cluster in which orf2 and orf3 have been deleted. Strain NMB and other meningococcal isolates which express class II type IV pili contained pgl clusters in which pglB had been replaced by pglB2 and an additional novel ORF, orf8, had been inserted between pglB2 and pglC. Insertional inactivation of the eight ORFs of the pgl cluster of strain NMB showed that pglF, pglB2, pglC, and pglD, but not orf2, orf3, orf8, and avtA, were necessary for pilin glycosylation. Pilin glycosylation was not essential for resistance to normal human serum, as pglF and pglD mutants retained wild-type levels of serum resistance. Although pglB2 and pglC mutants were significantly sensitive to normal human serum under the experimental conditions used, subsequent examination of the encapsulation phenotypes revealed that pglB2 and pglC mutants expressed almost 50% less capsule than wild-type NMB. A mutation in orf3, which did not affect pilin glycosylation, also resulted in a 10% reduction in capsule expression and a moderately serum sensitive phenotype. On the basis of these results we suggest that pilin glycosylation may proceed via a lipid-linked oligosaccharide intermediate and that blockages in this pathway may interfere with capsular transport or assembly.

SUBMITTER: Kahler CM

PROVIDER: S-EPMC98345 | biostudies-literature | 2001 Jun

REPOSITORIES: biostudies-literature

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Polymorphisms in pilin glycosylation Locus of Neisseria meningitidis expressing class II pili.

Kahler C M CM Martin L E LE Tzeng Y L YL Miller Y K YK Sharkey K K Stephens D S DS Davies J K JK

Infection and immunity 20010601 6

We have located a locus, pgl, in Neisseria meningitidis strain NMB required for the glycosylation of class II pili. Between five and eight open reading frames (ORFs) (pglF, pglB, pglC, pglB2, orf2, orf3, orf8, and avtA) were present in the pgl clusters of different meningococcal isolates. The Class I pilus-expressing strains Neisseria gonorrhoeae MS11 and N. meningitidis MC58 each contain a pgl cluster in which orf2 and orf3 have been deleted. Strain NMB and other meningococcal isolates which ex ...[more]

PMID: 11349019

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Project description:BackgroundNeisseria meningitidis expresses type four pili (Tfp) which are important for colonisation and virulence. Tfp have been considered as one of the most variable structures on the bacterial surface due to high frequency gene conversion, resulting in amino acid sequence variation of the major pilin subunit (PilE). Meningococci express either a class I or a class II pilE gene and recent work has indicated that class II pilins do not undergo antigenic variation, as class II pilE genes encode conserved pilin subunits. The purpose of this work was to use whole genome sequences to further investigate the frequency and variability of the class II pilE genes in meningococcal isolate collections.ResultsWe analysed over 600 publically available whole genome sequences of N. meningitidis isolates to determine the sequence and genomic organization of pilE. We confirmed that meningococcal strains belonging to a limited number of clonal complexes (ccs, namely cc1, cc5, cc8, cc11 and cc174) harbour a class II pilE gene which is conserved in terms of sequence and chromosomal context. We also identified pilS cassettes in all isolates with class II pilE, however, our analysis indicates that these do not serve as donor sequences for pilE/pilS recombination. Furthermore, our work reveals that the class II pilE locus lacks the DNA sequence motifs that enable (G4) or enhance (Sma/Cla repeat) pilin antigenic variation. Finally, through analysis of pilin genes in commensal Neisseria species we found that meningococcal class II pilE genes are closely related to pilE from Neisseria lactamica and Neisseria polysaccharea, suggesting horizontal transfer among these species.ConclusionsClass II pilins can be defined by their amino acid sequence and genomic context and are present in meningococcal isolates which have persisted and spread globally. The absence of G4 and Sma/Cla sequences adjacent to the class II pilE genes is consistent with the lack of pilin subunit variation in these isolates, although horizontal transfer may generate class II pilin diversity. This study supports the suggestion that high frequency antigenic variation of pilin is not universal in pathogenic Neisseria.

Project description:UnlabelledExpression of type four pili (Tfp) is essential for virulence in Neisseria meningitidis. Pili mediate adhesion, bacterial aggregation, and DNA uptake. In N. meningitidis, the major pilin subunit is encoded by the pilE gene. In some strains, PilE is subject to phase and antigenic variation, which can alter Tfp properties and together offer a possible mechanism of immune escape. Pilin expression and antigenic variation can be modulated in response to environmental cues; however, the precise mechanisms of such regulation remain unclear. We identified a promoter in the pilE locus, 3' of the pilE coding sequence, on the antisense (AS) strand which is conserved in meningococci. We show that this promoter directs transcription of an AS RNA that is expressed during specific growth phases and in response to salt stress. Furthermore, we demonstrate that the transcript encompasses sequences complementary to the entire pilE coding sequence and 5' untranslated region. AS RNAs can regulate the gene on the sense strand by altering transcript stability or translation. However, by using Northern blotting, quantitative reverse transcription-PCR (RT-PCR), and Western blotting, we found no significant AS RNA-dependent changes in pilE transcript or protein level. Instead, our data indicate that the AS RNA influences pilin antigenic variation. This work provides further insights into the complex regulation of pilin expression and variation in pathogenic Neisseria.ImportancePathogenic Neisseria spp. express type four pili (Tfp) which are important for adhesion, aggregation and transformation. Some strains of N. meningitidis are able to vary the sequence of the major subunit (PilE) of the Tfp. The mechanisms underlying this variation are not fully defined, but the process requires several noncoding elements that are found adjacent to the pilE gene. In this work, we identified a cis-encoded RNA antisense to pilE in N. meningitidis. By using Northern blotting and RT-PCR analysis, we found that the RNA is expressed in stationary phase or following salt stress. Our work also indicates that this RNA does not significantly affect pilE or pilin expression levels but instead appears to modulate pilin variation.

Dataset Information

Polymorphisms in pilin glycosylation Locus of Neisseria meningitidis expressing class II pili.

Publications

Polymorphisms in pilin glycosylation Locus of Neisseria meningitidis expressing class II pili.

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