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Found 2 structures.
Displayed structures from 1 to 2
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Structure type: homopolymer
Trivial name: poly-β-1,6-GlcNAc (PGA), biofilm, poly-b-(1-6)-N-acetyl-D-glucosamine (PNAG), poly-β-N-acetyl-glucosamine (PNAG), PNAG, poly-N-acetylglucosamine, PNAG
Compound class: CPS, EPS, O-polysaccharide, glucan, polysaccharide
Contained glycoepitopes: IEDB_135813,IEDB_137340,IEDB_141807,IEDB_151531,IEDB_753248
Staphylococcus aureus and Staphylococcus epidermidis often elaborate adherent biofilms, which contain the capsular polysaccharide-adhesin (PS/A) that mediates the initial cell adherence to biomaterials. Biofilm cells produce another antigen, termed polysaccharide intercellular adhesin (PIA), which is composed of a approximately 28 kDa soluble linear β(1-6)-linked N-acetylglucosamine. We developed a new method to purify PS/A from S. aureus MN8m, a strain hyperproducing PS/A. Using multiple analytical techniques, we determined that the chemical structure of PS/A is also β(1-6)-N-acetylglucosamine (PNAG). We were unable to find N-succinylglucosamine residues in any of our preparations in contrast to previously reported findings (D. McKenney, K. Pouliot, Y. Wang, V. Murthy, M. Ulrich, G. Doring, J. C. Lee, D. A Goldmann, and G. B. Pier, Science 284:1523-1527, 1999). PNAG was produced with a wide range of molecular masses that could be divided into three major fractions with average molecular masses of 460 kDa (PNAG-I), 100 kDa (PNAG-II), and 21 kDa (PNAG-III). The purified antigens were not soluble at neutral pH unless first dissolved in 5 M HCl and then neutralized with 5 M NaOH. PNAG-I was very immunogenic in rabbits, but the responses of individual animals were variable. Immunization of mice with various doses (100, 50, or 10 microg) of PNAG-I, -II, and -III demonstrated that only PNAG-I was able to elicit an immunoglobulin G (IgG) immune response with the highest titers obtained with 100-microg dose. When we purified a small fraction of PNAG with a molecular mass of approximately 780 kDa (PNAG-780) from PNAG-I, significantly higher IgG titers than those in mice immunized with the same doses of PNAG-I were obtained, suggesting the importance of the molecular mass of PNAG in the antibody response. These results further clarify the chemical structure of PS/A and help to differentiate it from PIA on the basis of immunogenicity, molecular size, and solubility.
NMR, Bacterial, Staphylococcus, Staphylococcus aureus, classification, adhesin, Opsonins, phagocytosis, surface polysaccharide
NCBI PubMed ID: 12117954Production of a polysaccharide matrix is a hallmark of bacterial biofilms, but the composition of matrix polysaccharides and their functions are not widely understood. Previous studies of the regulation of Escherichia coli biofilm formation suggested the involvement of an unknown adhesin. We now establish that the pgaABCD (formerly ycdSRQP) locus affects biofilm development by promoting abiotic surface binding and intercellular adhesion. All of the pga genes are required for optimal biofilm formation under a variety of growth conditions. A pga-dependent cell-bound polysaccharide was isolated and determined by nuclear magnetic resonance analyses to consist of unbranched β-1,6-N-acetyl-D-glucosamine, a polymer previously unknown from the gram-negative bacteria but involved in adhesion by staphylococci. The pga genes are predicted to encode envelope proteins involved in synthesis, translocation, and possibly surface docking of this polysaccharide. As predicted, if poly-β-1,6-GlcNAc (PGA) mediates cohesion, metaperiodate caused biofilm dispersal and the release of intact cells, whereas treatment with protease or other lytic enzymes had no effect. The pgaABCD operon exhibits features of a horizontally transferred locus and is present in a variety of eubacteria. Therefore, we propose that PGA serves as an adhesin that stabilizes biofilms of E. coli and other bacteria.
biosynthesis, gene, regulation, polysaccharides, adhesin, biofilms, phylogeny, PNAG
NCBI PubMed ID: 15090514Biofilms are composed of bacterial cells embedded in an extracellular polysaccharide matrix. A major component of the Escherichia coli biofilm matrix is PGA, a linear polymer of N-acetyl-d-glucosamine residues in β(1,6) linkage. PGA mediates intercellular adhesion and attachment of cells to abiotic surfaces. In this report, we present genetic and biochemical evidence that PGA is also a major matrix component of biofilms produced by the human periodontopathogen Actinobacillus actinomycetemcomitans and the porcine respiratory pathogen Actinobacillus pleuropneumoniae. We also show that PGA is a substrate for dispersin B, a biofilm-releasing glycosyl hydrolase produced by A. actinomycetemcomitans, and that an orthologous dispersin B enzyme is produced by A. pleuropneumoniae. We further show that A. actinomycetemcomitans PGA cross-reacts with antiserum raised against polysaccharide intercellular adhesin, a staphylococcal biofilm matrix polysaccharide that is genetically and structurally related to PGA. Our findings confirm that PGA functions as a biofilm matrix polysaccharide in phylogenetically diverse bacterial species and suggest that PGA may play a role in intercellular adhesion and cellular detachment and dispersal in A. actinomycetemcomitans and A. pleuropneumoniae biofilms.
gene, Escherichia, Escherichia coli, extracellular polysaccharide, adhesin, Actinobacillus, Actinobacillus actinomycetemcomitans, Actinobacillus pleuropneumoniae, biofilms
NCBI PubMed ID: 15576769Polymeric β-1,6-N-acetyl-D-glucosamine (poly-β-1,6-GlcNAc) has been implicated as an Escherichia coli and Staphylococcus epidermidis biofilm adhesin, the formation of which requires the pgaABCD and icaABCD loci, respectively. Enzymatic hydrolysis of poly-β-1,6-GlcNAc, demonstrated for the first time by chromatography and mass spectrometry, disrupts biofilm formation by these species and by Yersinia pestis and Pseudomonas fluorescens, which possess pgaABCD homologues
Bacterial, metabolism, microbiology, Non-U.S.Gov't, Pseudomonas, Research, Escherichia, Escherichia coli, immunology, hydrolysis, spectrometry, mass spectrometry, enzymatic, medicine, formation, Staphylococcus, Pseudomonas fluorescens, time, chromatography, operon, species, adhesin, depolymerization, Yersinia, Actinobacillus actinomycetemcomitans, Bacterial Adhesion, biofilms, U.S.Gov't, PDF, Staphylococcus epidermidis, Biofilm, enzymology, Yersinia pestis, physiology, P.H.S., enzymatic hydrolysis, Acetylglucosamine, β-N-Acetylhexosaminidase, Research Support
NCBI PubMed ID: 15601723Staphylococcus aureus and coagulase-negative staphylococci, primarily Staphylococcus epidermidis, are recognized as a major cause of nosocomial infections associated with the use of implanted medical devices. It has been established that clinical isolates often produce a biofilm, which is involved in adherence to biomaterials and provides enhanced resistance of bacteria against host defenses and antibiotic treatments. It has been thought that the staphylococcal biofilm contains two polysaccharides, one responsible for primary cell adherence to biomaterials (polysaccharide/adhesin [PS/A]) and an antigen that mediates bacterial aggregation (polysaccharide intercellular adhesin [PIA]). In the present paper we present an improved procedure for preparation of PIA that conserves its labile substituents and avoids contamination with by-products. Based on structural analysis of the polysaccharide antigens and a thorough overview of the previously published data, we concluded that PIA from S. epidermidis is structurally identical to the recently described poly-β-(1→6)-N-acetylglucosamine from PS/A-overproducing strain S. aureus MN8m. We also show that another carbohydrate-containing polymer, extracellular teichoic acid (EC TA), is an essential component of S. epidermidis RP62A biofilms. We demonstrate that the relative amounts of extracellular PIA and EC TA produced depend on the growth conditions. Moderate shaking or static culture in tryptic soy broth favors PIA production, while more EC TA is produced in brain heart infusion medium.
antigen, clinical, Bacterial, host, isolate, strain, structural, polysaccharide, analysis, cell, polymer, adherence, acid, antigens, enhanced, infection, bacteria, structural analysis, polysaccharides, production, Staphylococcus, Staphylococcus aureus, treatment, extracellular, component, preparation, teichoic acid, biotechnology, resistance, adhesin, culture, Polymers, polysaccharide antigen, biofilms, PDF, model, Staphylococcus epidermidis, Biofilm, France, medical, use, defense, host defense, medium, growth, labile, antibiotic, aggregation, brain, growth conditions, infusion, nosocomial infections
NCBI PubMed ID: 15845508Background. The staphylococcal surface polysaccharide poly N-acetyl glucosamine (PNAG) is a target for killing and protective antibody in animals. We investigated the human antibody response and specificity of binding and opsonic antibodies for different epitopes on PNAG in serum samples from patients with cystic fibrosis (CF) colonized and not colonized with Staphylococcus aureus.Methods. Serum samples from patients with CF colonized and not colonized with S. aureus were used to compare levels and specificities of binding and opsonic antibodies to native PNAG (>95% acetylation) and deacetylated PNAG (dPNAG, ~15% acetylation).Results. Colonized patients had higher killing activity mediated by opsonic antibody than did noncolonized patients in a PNAG-specific opsonophagocytic assay (P<.0001) but no difference in average levels of antibody to either PNAG or dPNAG by enzyme-linked immunosorbent assay. Killing activity in serum samples of the colonized patients correlated with the level of IgG specific to dPNAG more than to native PNAG. dPNAG and PNAG shared expression of the epitopes binding opsonic antibody, as evidenced by comparable inhibition of opsonophagocytic killing by both antigens. Affinity-purified antibodies specific to dPNAG were superior in mediating opsonic killing.Conclusion. Human antibodies to PNAG that mediate opsonic killing bind primarily to the nonacetylated epitopes of this antigen, which indicates that these antigenic determinants are the dominant targets of the functional human antibody response to staphylococcal PNAG.
antigen, expression, functional, human, role, polysaccharide, antigenic determinant, antibodies, antibody, epitope, animal, antibody response, antigens, IgG, level, response, epitopes, specific, specificity, activity, medicine, surface, Staphylococcus, inhibition, difference, antigenic, determinant, binding, serum, killing, surface polysaccharide, cystic fibrosis, acetylation, opsonic, protective, PNAG, assay, native, Glucosamine, epitope specificity, medical, enzyme-linked immunosorbent assay, immunosorbent, target, Animals, human antibodies, N-acetyl
NCBI PubMed ID: 16267775Staphylococcus aureus and Staphylococcus epidermidis both synthesize the surface polysaccharide poly-N-acetyl-β-(1-6)-glucosamine (PNAG), which is produced in vitro with a high level (>90%) of the amino groups substituted by acetate. Here, we examined the role of the acetate substituents of PNAG in generating opsonic and protective antibodies. PNAG and a deacetylated form of the antigen (dPNAG; 15% acetylation) were conjugated to the carrier protein diphtheria toxoid (DT) and used to immunize animals. Mice responded in a dose-dependent fashion to both conjugate vaccines, with maximum antibody titers observed at the highest dose and 4 weeks after the last of three weekly immunizations. PNAG-DT and dPNAG-DT vaccines were also very immunogenic in rabbits. Antibodies raised to the conjugate vaccines in rabbits mediated the opsonic killing of various staphylococcal strains, but the specificity of the opsonic killing was primarily to dPNAG, as this antigen inhibited the killing of S. aureus strains by both.
antigen, role, strain, polysaccharide, group, form, antibodies, antibody, animal, high, immunization, level, mice, protein, specificity, activity, medicine, surface, vaccines, Staphylococcus, Staphylococcus aureus, amino, amino group, vaccine, immunogenic, conjugate, conjugate vaccines, conjugate vaccine, killing, surface polysaccharide, acetylation, opsonic, protective, PNAG, native, Staphylococcus epidermidis, in vitro, rabbit, carrier, toxoid, Rabbits, diphtheria, Animals, acetate, diphtheria toxoid
NCBI PubMed ID: 16177353The RNA-binding protein CsrA represses biofilm formation, while the non-coding RNAs CsrB and CsrC activate this process by sequestering CsrA. We now provide evidence that the pgaABCD transcript, required for the synthesis of the polysaccharide adhesin PGA (poly-β-1,6-N-acetyl-d-glucosamine) of Escherichia coli, is the key target of biofilm regulation by CsrA. csrA disruption causes an approximately threefold increase in PGA production and an approximately sevenfold increase in expression of a pgaA'-'lacZ translational fusion. A ∆csrB∆csrC mutant exhibits a modest decrease in pgaA'-'lacZ expression, while the response regulator UvrY, a transcriptional activator of csrB and csrC, stimulates this expression. Biofilm formation is not regulated by csrA, csrB or uvrY in a ∆pgaC mutant, which cannot synthesize PGA. Gel mobility shift and toeprint analyses demonstrate that CsrA binds cooperatively to pgaA mRNA and competes with 30S ribosome subunit for binding. CsrA destabilizes the pgaA transcript in vivo. RNA footprinting and boundary analyses identify six apparent CsrA binding sites in the pgaA mRNA leader, the most extensive arrangement of such sites in any mRNA examined to date. Substitution mutations in CsrA binding sites overlapping the Shine-Dalgarno sequence and initiation codon partially relieve repression by CsrA. These studies define the crucial mechanisms, though not the only means, by which the Csr system influences biofilm formation
synthesis, expression, Gene Expression Regulation, Bacterial, genetics, growth & development, metabolism, microbiology, polysaccharide, Research, Escherichia, Escherichia coli, immunology, Molecular Sequence Data, protein, regulation, response, mutant, polysaccharides, production, mechanism, medicine, sequence, mutation, formation, binding, binding site, site, repression, RNA, Base Sequence, adhesin, biofilms, U.S.Gov't, decrease, Biofilm, mobility, substitution, influence, shift, P.H.S., gel, target, mRNA, in vivo, initiation, Research Support, fusion, Adhesins, Binding Sites, Escherichia coli Proteins, regulator, Repressor Proteins, N.I.H., Extramural, RNA-Binding Proteins
NCBI PubMed ID: 15916613Bordetellae are Gram-negative bacteria which colonize the respiratory tract of animals and humans. We and others have recently shown that these bacteria are capable of living as sessile communities known as biofilms on a number of abiotic surfaces. During the biofilm mode of existence, bacteria produce one or more extracellular polymeric substances which function in part, to hold the cells together and to a surface. There is little information on either the constituents of the biofilm matrix or the genetic basis of biofilm development by Bordetella. By utilizing immunoblot assays and by enzymatic hydrolysis using Dispersin B (DspB), a glycosyl hydrolase that specifically cleaves the polysaccharide, poly-β-1,6-N-acetyl-D-glucosamine (GlcNAc), we provide evidence for the production of poly-β-1,6-GlcNAc by various Bordetella species (B. bronchiseptica, B. pertussis and B. parapertussis) and its role in their biofilm development. We have investigated the role of a Bordetella locus designated herein as bpsABCD (Bordetella polysaccharide) in biofilm formation. The bps locus is homologous to several bacterial loci that are required for the production of poly-β-1,6-GlcNAc and have been implicated in bacterial biofilm formation. By utilizing multiple microscopic techniques to analyze biofilm formation under both static and hydrodynamic conditions, we demonstrate that the bps locus although not essential at initial stages of biofilm formation, contributes to the stability and the maintenance of the complex architecture of Bordetella biofilms
Bordetella, molecular genetics, Biofilm
NCBI PubMed ID: 17114249Poly-N-acetyl-glucosamine (PNAG) is a staphylococcal surface polysaccharide influencing biofilm formation that is also under investigation for its vaccine potential. Antibodies that bind to PNAG with either low (<15%) or high (>90%) levels of acetate are superior at opsonic and protective activity compared with antibodies that bind to PNAG with only high levels (>70%) of acetate. PNAG is synthesized by four proteins encoded within the intercellular adhesin (ica) locus icaADBC. In Staphylococcus epidermidis, icaB encodes a deacetylase needed for the surface retention of PNAG and optimal biofilm formation. In this study, we confirmed that icaB plays a similar role in Staphylococcus aureus and found that an icaB mutant of S. aureus expressed significantly less surface-associated PNAG, was highly susceptible to antibody-independent opsonic killing that could not be enhanced with antibody raised against deacetylated PNAG (dPNAG), and had reduced survival capacity in a murine model of bacteremia. In contrast, an icaB-overexpressing strain produced primarily surface-associated PNAG, was more susceptible to opsonophagocytosis with antibody to dPNAG, and had increased survival in a murine bacteremia model. The highly acetylated secreted PNAG was more effective at blocking opsonic killing mediated by a human monoclonal antibody (mAb) to native PNAG than it was at blocking killing mediated by a human mAb to dPNAG, which by itself was a more effective opsonin. Retention of dPNAG on the surface of S. aureus is key to increased survival during bacteremia and also provides a molecular mechanism explaining the superior opsonic and protective activity of antibody to dPNAG
antibodies, Staphylococcus aureus, Acetylglucosamine, Amidohydrolases, Bacterial bacteremia
NCBI PubMed ID: 17470540Biofilm formation in Staphylococcus aureus is usually associated with the production of the poly-N-acetylglucosamine PNAG) exopolysaccharide, synthesized by proteins encoded by the icaADBC operon. PNAG is a linear β-(1-6)-linked N-acetylglucosaminoglycan that has to be partially deacetylated and consequently positively charged in order to be associated with bacterial cell surfaces. Here, we investigated whether attachment of PNAG to bacterial surfaces is mediated by ionic interactions with the negative charge of wall teichoic acids (WTAs), which represent the most abundant polyanions of the Gram-positive bacterial envelope. We generated WTA-deficient mutants by in-frame deletion of the tagO gene in two genetically unrelated S. aureus strains. The ∆tagO mutants were more sensitive to high temperatures, showed a higher degree of cell aggregation, had reduced initial adherence to abiotic surfaces and had a reduced capacity to form biofilms under both steady-state and flow conditions. However, the levels as well as the strength of the PNAG interaction with the bacterial cell surface were similar between ∆tagO mutants and their corresponding wild-type strains. Furthermore, double ∆tagO ∆icaADBC mutants displayed a similar aggregative phenotype to that of single ∆tagO mutants, indicating that PNAG is not responsible for the aggregative behaviour observed in ∆tagO mutants. Overall, the absence of WTAs in S. aureus had little effect on PNAG production or anchoring to the cell surface, but did affect the biofilm-forming capacity, cell aggregative behaviour and the temperature sensitivity/stability of S. aureus.
exopolysaccharide, Staphylococcus, Staphylococcus aureus, teichoic acid, PNAG, Biofilm, cell aggregation
NCBI PubMed ID: 18310032We found that Acinetobacter baumannii contains a pgaABCD locus that encodes proteins that synthesize cell-associated poly-β-(1-6)-N-acetylglucosamine (PNAG). Both a mutant with an in-frame deletion of the pga locus (S1∆pga) and a transcomplemented strain (S1∆pga-c) of A. baumannii were constructed, and the PNAG production by these strains was compared using an immunoblot assay. Deleting the pga locus resulted in an A. baumannii strain without PNAG, and transcomplementation of the S1∆pga strain with the pgaABCD genes fully restored the wild-type PNAG phenotype. Heterologous expression of the A. baumannii pga locus in Escherichia coli led to synthesis of significant amounts of PNAG, while no polysaccharide was detected in E. coli cells harboring an empty vector. Nuclear magnetic resonance analysis of the extracellular polysaccharide material isolated from A. baumannii confirmed that it was PNAG, but notably only 60% of the glucosamine amino groups were acetylated. PCR analysis indicated that all 30 clinical A. baumannii isolates examined had the pga genes, and immunoblot assays indicated that 14 of the 30 strains strongly produced PNAG, 14 of the strains moderately to weakly produced PNAG, and 2 strains appeared to not produce PNAG. Deletion of the pga locus led to loss of the strong biofilm phenotype, which was restored by complementation. Confocal laser scanning microscopy studies combined with COMSTAT analysis demonstrated that the biovolume, mean thickness, and maximum thickness of 16-h and 48-h-old biofilms formed by wild-type and pga-complemented A. baumannii strains were significantly greater than the biovolume, mean thickness, and maximum thickness of 16-h and 48-h-old biofilms formed by the S1∆pga mutant strain. Biofilm-dependent production of PNAG could be an important virulence factor for this emerging pathogen that has few known virulence factors
Bacterial Proteins, Gene Expression Regulation, Bacterial, Acinetobacter baumannii, biofilms, beta-glucans
NCBI PubMed ID: 19633088We demonstrated the production of poly-β-1,6-N-acetylglucosamine (PNAG) polysaccharide in the biofilms of Burkholderia multivorans, Burkholderia vietnamiensis, Burkholderia ambifaria, Burkholderia cepacia, and Burkholderia cenocepacia using an immunoblot assay for PNAG. These results were confirmed by further studies, which showed that the PNAG hydrolase, dispersin B, eliminated immunoreactivity of extracts from the species that were tested (B. cenocepacia and B. multivorans). Dispersin B also inhibited biofilm formation and dispersed preformed biofilms of Burkholderia species. These results imply a role for PNAG in the maintenance of Burkholderia biofilm integrity. While PNAG was present in biofilms of all of the wild-type test organisms, a ∆pgaBC mutant of B. multivorans (Mu5) produced no detectable PNAG, indicating that these genes are needed for Burkholderia PNAG formation. Furthermore, restoration of PNAG production in PNAG negative E. coli TRXWMG∆C (∆pgaC) by complementation with B. multivorans pgaBCD confirmed the involvement of these genes in Burkholderia PNAG production. While the confocal scanning laser microscopy of untreated wild-type B. multivorans showed thick, multilayered biofilm, Mu5 and dispersin B-treated wild-type biofilms were thin, poorly developed, and disrupted, confirming the involvement of PNAG in B. multivorans biofilm formation. Thus, PNAG appears to be an important component of Burkholderia biofilms, potentially contributing to its resistance to multiple antibiotics and persistence during chronic infections, including cystic fibrosis-associated infection.
Burkholderia, Burkholderia cepacia, biofilms, PNAG, Burkholderia vietnamiensis, Burkholderia cenocepacia
NCBI PubMed ID: 21984237Bordetella are Gram negative respiratory pathogens of animals, birds and humans. A hallmark feature of some Bordetella species is their ability to efficiently survive in the respiratory tract even after vaccination. B. bronchiseptica and B. pertussis form biofilms on abiotic surfaces and in the mouse respiratory tract. The Bps exopolysaccharide is one of the critical determinants for biofilm formation and the survival of Bordetella in the murine respiratory tract. In order to gain a better understanding of regulation of biofilm formation, we sought to study the mechanism by which Bps expression is controlled in Bordetella. Expression of bpsA-D is elevated in biofilms compared with planktonically grown cells. We found that bpsA-D is expressed independent of BvgAS. Subsequently, we identified an ORF BB1771, (designated herein, bpsR) that is located upstream and in the opposite orientation to the bpsA-D locus. BpsR is homologous to the MarR-family of transcriptional regulators. Measurement of bpsA and bpsD transcripts and the Bps polysaccharide levels from the wild-type and the ∆bpsR strains suggested that BpsR functions as a repressor. Consistent with enhanced production of Bps, the bpsR mutant displayed considerably more structured biofilms. We mapped the bpsA-D promoter region and show that purified BpsR protein specifically bound to the bpsA-D promoter. Our results provide mechanistic insights into the regulatory strategy employed by Bordetella for control of the production of the Bps polysaccharide and biofilm formation.
protein, Bordetella, exopolysaccharide, Biofilm
NCBI PubMed ID: 22056934Background New therapeutic targets for antibiotic-resistant bacterial pathogens are desperately needed. The bacterial surface polysaccharide poly-β-(1-6)-N-acetyl-glucosamine (PNAG) mediates biofilm formation by some bacterial species, and antibodies to PNAG can confer protective immunity. By analyzing sequenced genomes, we found that potentially multidrug-resistant bacterial species such as Klebsiella pneumoniae, Enterobacter cloacae, Stenotrophomonas maltophilia, and the Burkholderia cepacia complex (BCC) may be able to produce PNAG. Among patients with cystic fibrosis patients, highly antibiotic-resistant bacteria in the BCC have emerged as problematic pathogens, providing an impetus to study the potential of PNAG to be targeted for immunotherapy against pan-resistant bacterial pathogens. Methods The presence of PNAG on BCC was assessed using a combination of bacterial genetics, microscopy, and immunochemical approaches. Antibodies to PNAG were tested using opsonophagocytic assays and for protective efficacy against lethal peritonitis in mice. Results PNAG is expressed in vitro and in vivo by the BCC, and cystic fibrosis patients infected by the BCC species B. dolosa mounted a PNAG-specific opsonophagocytic antibody response. Antisera to PNAG mediated opsonophagocytic killing of BCC and were protective against lethal BCC peritonitis even during coinfection with methicillin-resistant Staphylococcus aureus. Conclusions Our findings raise potential new therapeutic options against PNAG-producing bacteria, including even pan-resistant pathogens.
antibodies, PNAG, Biofilm, protective immunity, Burkholderia cepacia complex (BCC), opsonophagocytic assays
NCBI PubMed ID: 22448004Many medically important biofilm forming bacteria produce similar polysaccharide intercellular adhesins (PIA) consisting of partially de-N-acetylated β-(1→6)-N-acetylglucosamine polymers (dPNAG). In Escherichia coli, de-N-acetylation of the β-(1→6)-N-acetylglucosamine polymer (PNAG) is catalysed by the carbohydrate esterase family 4 deacetylase PgaB. The de-N-acetylation of PNAG is essential for productive PNAG-dependent biofilm formation. Here, we describe the development of a fluorogenic assay to monitor PgaB activity in vitro and the synthesis of a series of PgaB inhibitors. The synthesized inhibitors consist of a metal chelating functional group on a glucosamine scaffold to target the active site metal ion of PgaB. Optimal inhibition was observed with N-thioglycolyl amide (K(i) = 480 muM) and N-methyl-N-glycolyl amide (K(i) = 320 muM) glucosamine derivatives. A chemoenzymatic synthesis of an N-thioglycolyl amide PNAG pentasaccharide led to an inhibitor with an improved K(i) of 280 muM.
synthesis, Escherichia coli, adhesin, biofilms, PNAG, inhibitor, PIA
NCBI PubMed ID: 22855025A polymer of partially de-N-acetylated -1,6-linked N-acetylglucosamine (dPNAG), also known as polysaccharide intercellular adhesin (PIA), is an important component of many bacterial biofilm matrices. In Staphyloccocus epidermidis, the poly-N-acetylglucosamine polymer is partially de-N-acetylated by the extracellular protein IcaB. To understand the mechanism of action of IcaB, the enzyme was overexpressed and purified. IcaB demonstrates metal dependent de-N-acetylase activity on -1,6-linked N-acetylglucosamine oligomers with a broad preference for divalent metals. Steady-state kinetic analysis reveals the low catalytic efficiency (pentasaccharide kcat/KM 0.03 M-1s-1) of the enzyme towards the oligomeric substrates. While IcaB displays similar rates of de-N-acetylation with tri- through hexasaccharide PNAG oligomers, position specific de-N-acetylation was only observed with penta- and hexasaccharides. The enzyme preferentially de-N-acetylates the second residue from the reducing terminus in the pentasaccharide, and second and third residues from the reducing terminus in the hexasaccharide. The data described here represents an important step towards a detailed understanding of dPNAG biosynthesis in S. epidermidis, an important nosocomial pathogen, as well as in other Gram-positive bacteria. The low catalytic activity of IcaB is consistent with reports of other enzymes which act on biofilm related polysaccharides and this emerging trend may indicate a common feature among this group of polysaccharide processing enzymes.
biosynthesis, Staphylococcus epidermidis, Biofilm, IcaB
NCBI PubMed ID: 23866051The emergence of extreme and pan-resistant gram-negative bacilli, such as Acinetobacter baumannii requires consideration of non-antimicrobial therapeutic approaches. The goal of this report was to evaluate the K1 capsular polysaccharide from A. baumannii as a passive immunization target. Its structure was determined by a combination of mass spectrometric and NMR techniques. Molecular mimics that might raise the concern for autoimmune disease were not identified. Immunization of CD1 mice demonstrated that the K1 capsule is immunogenic. The monoclonal antibody MAb13D6, which is directed against the K1 capsule from A. baumannii, was used to determine the seroprevalence of the K1 capsule in a collection of 100 A. baumannii strains. Thirteen percent of the A. baumannii isolates from this collection were seroreactive to MAb13D6. Opsonization of K1-positive strains, but not K1-minus strains, with MAb13D6 significantly increased neutrophil-mediated bactericidal activity in vitro (P < 0.05). Lastly, treatment with MAb13D6 three and twenty-four h after bacterial challenge in a rat soft-tissue infection model resulted in a significant decrease in the growth/survival a K1-positive strain compared to a K1-minus strain or to treatment with a vehicle control (P <0.0001). These data support the proof of principle that the K1 capsule is a potential therapeutic target via passive immunization. Other serotypes require assessment and pragmatic challenges exist such as the need to serotype infecting strains and utilize serotype-specific therapy. Nonetheless, this approach may become an important therapeutic option with increasing antimicrobial resistance and a diminishing number of active antimicrobials.
Acinetobacter baumannii, monoclonal antibodies, immunization, serotype-specific, capsular polysaccharid
NCBI PubMed ID: 23297385The biosynthesis and export of bacterial cell-surface polysaccharides is known to occur through several distinct mechanisms. Recent advances in the biochemistry and structural biology of several proteins in synthase-dependent polysaccharide secretion systems have identified key conserved components of this pathway in Gram-negative bacteria. These components include an inner-membrane-embedded polysaccharide synthase, a periplasmic tetratricopeptide repeat (TPR)-containing scaffold protein, and an outer-membrane beta-barrel porin. There is also increasing evidence that many synthase-dependent systems are post-translationally regulated by the bacterial second messenger bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP). Here, we compare these core proteins in the context of the alginate, cellulose, and poly-β-D-N-acetylglucosamine (PNAG) secretion systems.
exopolysaccharide, alginate, cellulose, synthase, poly-β-D-N-acetylglucosamine
NCBI PubMed ID: 23117123The emergence of multidrug-resistance Acinetobacter baumannii requires novel approaches for prevention, treatment and diagnosis. The structures of surface polysaccharides from A. baumannii are valuable tools to understand pathogenesis, virulence and immunogenicity. The synthesis of bacterial mono- or polysaccharides may result in novel probes to become important therapeutic options in the fight against A. baumannii. This report exemplifies the relevance of glycochemistry for the development of new antibiotics.
lipopolysaccharides, capsular polysaccharides, Acinetobacter, Acinetobacter baumannii, polysaccharide synthesis, surface polysaccharides
NCBI PubMed ID: 26531136Cell surface carbohydrates have been proven optimal targets for vaccine development. Conjugation of polysaccharides to a carrier protein triggers a T-cell dependent immune response to the glycan moiety. Licensed glycoconjugate vaccines are produced by chemical conjugation of capsular polysaccharides to prevent meningitis caused by meningococcus, pneumococcus and Haemophilus influenzae type b. However, other classes of carbohydrates (O-antigens, exopolysaccharides, wall/teichoic acids) represent attractive targets for developing vaccines.Recent analysis from WHO/CHO underpins alarming concern towards antibiotic resistant bacteria, such as the so called ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter spp.) and additional pathogens such as Clostridium difficile and Group A Streptococcus. Fungal infections are also becoming increasingly invasive for immunocompromised patients or hospitalized individuals. Other emergencies could derive from bacteria which spread during environmental calamities (Vibrio cholerae) or with potential as bioterrorism weapons (Burkholderia pseudomallei and mallei, Francisella tularensis). Vaccination could aid reducing the use of broad spectrum antibiotics and provide protection by herd immunity also to individuals who are not vaccinated.This review analyses structural and functional differences of the polysaccharides exposed on the surface of emerging pathogenic bacteria, combined with medical need and technological feasibility of corresponding glycoconjugate vaccines.
carbohydrates, glycoconjugates, vaccines, glycoengineering, antimicrobial resistance
NCBI PubMed ID: 29547971The O-acetylation of polysaccharides is a common modification used by pathogenic organisms to protect against external forces. Pseudomonas aeruginosa secretes the anionic, O-acetylated exopolysaccharide alginate during chronic infection in the lungs of cystic fibrosis patients to form the major constituent of a protective biofilm matrix. Four proteins have been implicated in the O-acetylation of alginate, AlgIJF and AlgX. To probe the biological function of AlgJ, we determined its structure to 1.83 Å resolution. AlgJ is a SGNH hydrolase-like protein, which while structurally similar to the N-terminal domain of AlgX exhibits a distinctly different electrostatic surface potential. Consistent with other SGNH hydrolases, we identified a conserved catalytic triad composed of D190, H192 and S288 and demonstrated that AlgJ exhibits acetylesterase activity in vitro. Residues in the AlgJ signature motifs were found to form an extensive network of interactions that are critical for O-acetylation of alginate in vivo. Using two different electrospray ionization mass spectrometry (ESI-MS) assays we compared the abilities of AlgJ and AlgX to bind and acetylate alginate. Binding studies using defined length polymannuronic acid revealed that AlgJ exhibits either weak or no detectable polymer binding while AlgX binds polymannuronic acid specifically in a length-dependent manner. Additionally, AlgX was capable of utilizing the surrogate acetyl-donor 4-nitrophenyl acetate to catalyze the O-acetylation of polymannuronic acid. Our results, combined with previously published in vivo data, suggest that the annotated O-acetyltransferases AlgJ and AlgX have separate and distinct roles in O-acetylation. Our refined model for alginate acetylation places AlgX as the terminal acetlytransferase and provides a rationale for the variability in the number of proteins required for polysaccharide O-acetylation.
mucoid pseudomonas-aeruginosa, o-acetylpeptidoglycan esterase, biosynthetic gene-cluster, biofilm formation
NCBI PubMed ID: 25165982The β-1–6-linked poly-N-acetylglucosamine (PNAG) polymer is a conserved surface polysaccharide produced by many bacteria, fungi, and protozoan (and even filarial) parasites. This wide-ranging expression makes PNAG an attractive target for vaccine development, as it potentially encompasses a broad range of microorganisms. Significant progress has been made in discovering important properties of the biology of PNAG expression in recent years. The molecular characterization and regulation of operons for the production of PNAG biosynthetic proteins and enzymes have been studied in many bacteria. In addition, the physiological function of PNAG has been further elucidated. PNAG-based vaccines and PNAG-targeting antibodies have shown great efficacy in preclinical research. Furthermore, clinical tests for both vaccines and antibodies have been carried out in humans and economically important animals, and the results are promising. Although it is not destined to be a smooth road, we are optimistic about new vaccines and immunotherapeutics targeting PNAG becoming validated and eventually licensed for clinical use against multiple infectious agents
monoclonal antibody, conjugate vaccine, poly-N-acetylglucosamine
Publication DOI: 10.1016/j.eng.2023.09.012| -6)-b-D-GlcpNAc-(1- | Show graphically |
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Structure type: homopolymer
; n=9
Aglycon: 3-(4-(acetylthio)butyrylamino)propyl or spacer + carrier protein (Tetanus Toxoid)
Trivial name: PNAG
Contained glycoepitopes: IEDB_135813,IEDB_137340,IEDB_141807,IEDB_151531,IEDB_753248
The emergence of multidrug-resistance Acinetobacter baumannii requires novel approaches for prevention, treatment and diagnosis. The structures of surface polysaccharides from A. baumannii are valuable tools to understand pathogenesis, virulence and immunogenicity. The synthesis of bacterial mono- or polysaccharides may result in novel probes to become important therapeutic options in the fight against A. baumannii. This report exemplifies the relevance of glycochemistry for the development of new antibiotics.
lipopolysaccharides, capsular polysaccharides, Acinetobacter, Acinetobacter baumannii, polysaccharide synthesis, surface polysaccharides
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