Bioinformatic insights into the biosynthesis of the Group B carbohydrate in Streptococcus agalactiae

Sutcliffe, Iain C.; Black, Gary W.; Harrington, Dean J.

doi:10.1099/mic.0.2007/014522-0

Cited by 30 publications

(34 citation statements)

References 69 publications

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“…Although this structure with phosphate in the polymer backbone is reminiscent of the teichoic acid structures (39), it does not contain typical polyols (i.e. glycerol, ribitol, and glucitol) found in the "classical" teichoic acids (2,39) or in the teichoic acid-like polymer (40). Consequently, the PS characterized in this study can be qualified as a sugar-phosphate cell-wall PS (41,42).…”

Section: Discussionmentioning

confidence: 89%

“…Outside of the Lactococcus genus, homologs of llmg_0226 or llmg_0227 were only identified in the genome of the opportunistic pathogen Streptococcus agalactiae (group B streptococcus) (43). Interestingly, the corresponding genes in group B streptococcus are located in a locus that could be involved in the synthesis of the group B antigen, a cell wall-anchored polysaccharide used to type this species (40).…”

Section: Discussionmentioning

confidence: 99%

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Cell Surface of Lactococcus lactis Is Covered by a Protective Polysaccharide Pellicle

Chapot‐Chartier

Vinogradov²,

Sadovskaya³

et al. 2010

Journal of Biological Chemistry

150

205

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In Gram-positive bacteria, the functional role of surface polysaccharides (PS) that are not of capsular nature remains poorly understood. Here, we report the presence of a novel cell wall PS pellicle on the surface of Lactococcus lactis. Spontaneous PS-negative mutants were selected using semi-liquid growth conditions, and all mutations were mapped in a single chromosomal locus coding for PS biosynthesis. PS molecules were shown to be composed of hexasaccharide phosphate repeating units that are distinct from other bacterial PS. Using complementary atomic force and transmission electron microscopy techniques, we showed that the PS layer forms an outer pellicle surrounding the cell. Notably, we found that this cell wall layer confers a protective barrier against host phagocytosis by murine macrophages. Altogether, our results suggest that the PS pellicle could represent a new cell envelope structural component of Gram-positive bacteria.

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Section: Discussionmentioning

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Cell Surface of Lactococcus lactis Is Covered by a Protective Polysaccharide Pellicle

Chapot‐Chartier

Vinogradov²,

Sadovskaya³

et al. 2010

Journal of Biological Chemistry

150

205

View full text Add to dashboard Cite

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“…Analogous to a bioinformatic analysis of group B Streptococcus (GBS) (Sutcliffe et al 2008), we searched the GAS chromosome for clusters enriched in genes encoding rhamnosepolysaccharide-related proteins, and identified a putative 12-gene GAC biosynthesis locus (Figure 1A) that is completely conserved among all sequenced GAS genomes published to date. Many of these genes, herein designated gacABCDEFGHIJKL , are predicted to encode proteins with functional annotations as glycosyltransferases (including rhamnosyltransferases) and polysaccharide transport proteins (Figure 1A).…”

Section: Resultsmentioning

confidence: 99%

The Classical Lancefield Antigen of Group A Streptococcus Is a Virulence Determinant with Implications for Vaccine Design

Sorge

Cole

Kuipers

et al. 2014

Cell Host & Microbe

129

251

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SUMMARY Group A Streptococcus (GAS) is a leading cause of infection-related mortality in humans. All GAS serotypes express the Lancefield group A carbohydrate (GAC), comprising a polyrhamnose backbone with an immunodominant N-acetylglucosamine (GlcNAc) side chain, which is the basis of rapid diagnostic tests. No biological function has been attributed to this conserved antigen. Here we identify and characterize the GAC biosynthesis genes,gacA-L. An isogenic mutant of the glycosyltransferase gacI, which is defective for GlcNAcside chain addition, is attenuated for virulence in two infection models, in association with increased sensitivity to neutrophil killing, platelet-derived antimicrobials in serum and the cathelicidin antimicrobial peptide LL-37. Antibodies to GAC lacking the GlcNAc side chain and containing only polyrhamnose promoted opsonophagocytic killing of multiple GAS serotypes and protected against systemic GAS challenge after passive immunization. Thus, the Lancefield antigen plays a functional role in GAS pathogenesis and its understanding has implications for vaccine development.

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“…As opposed to the PI-1 and PI-2a pili characterized in GBS, no regulatory gene was found in the vicinity of PI-2b locus (S1 Fig). Immediately upstream from the PI-2b operon lies another large operon of 16 genes ( sak1438 - 1460 in A909) proposed to encode the group B carbohydrate also known as antigen B (AgB) [16]. …”

Section: Resultsmentioning

confidence: 99%

Regulation of PI-2b Pilus Expression in Hypervirulent Streptococcus agalactiae ST-17 BM110

et al. 2017

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The widely spread Streptococcus agalactiae (also known as Group B Streptococcus, GBS) “hypervirulent” ST17 clone is strongly associated with neonatal meningitis. The PI-2b locus is mainly found in ST17 strains but is also present in a few non ST17 human isolates such as the ST-7 prototype strain A909. Here, we analysed the expression of the PI-2b pilus in the ST17 strain BM110 as compared to the non ST17 A909. Comparative genome analyses revealed the presence of a 43-base pair (bp) hairpin-like structure in the upstream region of PI-2b operon in all 26 ST17 genomes, which was absent in the 8 non-ST17 strains carrying the PI-2b locus. Deletion of this 43-bp sequence in strain BM110 resulted in a 3- to 5-fold increased transcription of PI-2b. Characterization of PI-2b promoter region in A909 and BM110 strains was carried out by RNAseq, primer extension, qRT-PCR and transcriptional fusions with gfp as reporter gene. Our results indicate the presence of a single promoter (Ppi2b) with a transcriptional start site (TSS) mapped 37 bases upstream of the start codon of the first PI-2b gene. The large operon of 16 genes located upstream of PI-2b codes for the group B carbohydrate (also known as antigen B), a major constituent of the bacterial cell wall. We showed that the hairpin sequence located between antigen B and PI-2b operons is a transcriptional terminator. In A909, increased expression of PI-2b probably results from read-through transcription from antigen B operon. In addition, we showed that an extended 5’ promoter region is required for maximal transcription of gfp as a reporter gene in S. agalactiae from Ppi2b promoter. Gene reporter assays performed in Lactococcus lactis strain NZ9000, a related non-pathogenic Gram-positive species, revealed that GBS-specific regulatory factors are required to drive PI-2b transcription. PI-2b expression is up-regulated in the BM110ΔcovR mutant as compared to the parental BM110 strain, but this effect is probably indirect. Collectively, our results indicate that PI-2b expression is regulated in GBS ST17 strains, which may confer a selective advantage in the human host either by reducing host immune responses and/or increasing their dissemination potential.

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Bioinformatic insights into the biosynthesis of the Group B carbohydrate in Streptococcus agalactiae

Cited by 30 publications

References 69 publications

Cell Surface of Lactococcus lactis Is Covered by a Protective Polysaccharide Pellicle

Cell Surface of Lactococcus lactis Is Covered by a Protective Polysaccharide Pellicle

The Classical Lancefield Antigen of Group A Streptococcus Is a Virulence Determinant with Implications for Vaccine Design

Regulation of PI-2b Pilus Expression in Hypervirulent Streptococcus agalactiae ST-17 BM110

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