Structure of a novel exopolysaccharide produced by Burkholderia vietnamiensis, a cystic fibrosis opportunistic pathogen

Burkholderia vietnamiensis belongs to the Burkholderia cepacia complex and is an opportunistic pathogen for cystic fibrosis patients. As many other Burkholderia species, it has a mucoide phenotype, producing abundant exopolysaccharide. In general, polysaccharides contribute to bacterial survival in a hostile environment, are recognised as virulence factors and as important components in biofilm formation. The primary structure of the exopolysaccharide produced by B. vietnamiensis LMG 10929 was determined mainly by use of 1D and 2D NMR spectroscopy and ESI mass spectrometry. The polymer consists of the trisaccharidic backbone 3)-beta-D-Glcp-(1\u21924)-alfa-D-Glcp-(1\u21923)-alfa-L-Fucp-(1\u2192 with the side chain alfa-D-Glcp-(1\u21924)-alfa-D-GlcAp-(1\u21923)-alfa-L-Fucp-(1\u2192 linked to C-3 of the alfa-D-Glcp residue. The polysaccharide also bears acetyl substituents on about 20% of its repeating units and on at least two different positions. The presence of fucose residues is a novel structural feature among the exopolysaccharides produced by species of the B. cepacia complex

Activity of antimicrobial peptides in the presence of polysaccharides produced by pulmonary pathogens.

Antimicrobial peptides (AMPs) are secreted in the airway and contribute to initial defence against inhaled pathogens. Infections of the respiratory tract are a major cause of morbidity and mortality in preterm newborns and in patients with cystic fibrosis (CF). In this latter group, the state of chronic lung infection is due to the ability of bacteria to grow as mucoid biofilm, a condition characterised by overproduction and release of polysaccharides (PSs). In this study, we investigate the effect of PSs produced by lung pathogens such as Pseudomonas aeruginosa, Klebsiella pneumoniae andmembers of the Burkholderia cepacia complex on the antibacterial activity of structurally different peptides. The AMPs tested in this study include the cathelicidin LL-37 and the \u3b2-defensin hBD-3 from humans, both released at the alveolar level, as well as peptides from other mammals, i.e. SMAP-29, PG-1 and Bac7(1-35). Susceptibility assays, time killing and membrane permeabilization kinetics experiments were carried out to establish whether PSs produced by lung pathogens may be involved in the poor defence reaction of infected lungs and thus explain infection persistence. All the PSs investigated inhibited, albeit to a different extent, the antibacterial activity of the peptides tested, suggesting that their presence in the lungs of patients with CF may contribute to the decreased defence response of this district upon infection by PS-producing microorganisms. The results also show that inhibition of the antibacterial activity is not simply due to ionic interaction between the negatively charged PSs and the cationic AMPs, but it also involves other structural features of both interactors

Versatility of the Burkholderia cepacia Complex for the biosynthesis of exopolysaccharides: a comparative structural investigation

The Burkholderia cepacia Complex assembles at least eighteen closely related species that are ubiquitous in nature. Some isolates show beneficial potential for biocontrol, bioremediation and plant growth promotion. On the contrary, other strains are pathogens for plants and immunocompromised individuals, like cystic fibrosis patients. In these subjects, they can cause respiratory tract infections sometimes characterised by fatal outcome. Most of the Burkholderia cepacia Complex species are mucoid when grown on a mannitol rich medium and they also form biofilms, two related characteristics, since polysaccharides are important component of biofilm matrices. Moreover, polysaccharides contribute to bacterial survival in a hostile environment by inhibiting both neutrophils chemotaxis and antimicrobial peptides activity, and by scavenging reactive oxygen species. The ability of these microorganisms to produce exopolysaccharides with different structures is testified by numerous articles in the literature. However, little is known about the type of polysaccharides produced in biofilms and their relationship with those obtained in non-biofilm conditions. The aim of this study was to define the type of exopolysaccharides produced by nine species of the Burkholderia cepacia Complex. Two isolates were then selected to compare the polysaccharides produced on agar plates with those formed in biofilms developed on cellulose membranes. The investigation was conducted using NMR spectroscopy, high performance size exclusion chromatography, and gas chromatography coupled to mass spectrometry. The results showed that the Complex is capable of producing a variety of exopolysaccharides, most often in mixture, and that the most common exopolysaccharide is always cepacian. In addition, two novel polysaccharide structures were determined: one composed of mannose and rhamnose and another containing galactose and glucuronic acid. Comparison of exopolysaccharides obtained from cultures on agar plates with those extracted from biofilms on cellulose membranes showed important differences, thus suggesting that extrapolating data from non-biofilm conditions might not always be applicable

Exopolysaccharides produced by clinical strains belonging to the Burkholderia cepacia complex

Background: In the frame of a research line dedicated to better clarify the role of exopolysaccharides (EPS) in bacterial virulence, EPS produced by species of the Burkholderia cepacia complex (Bcc), namely Burkholderia multivorans, Burkholderia cenocepacia, and a Bcc member of undetermined genomovar, all isolated at the Cystic Fibrosis Regional Centre of Florence (Italy), were investigated for they structural properties. Methods: Three strains of B. multivorans, three of B. cenocepacia and one of a Bcc member of undetermined genomovar were isolated from CF patients. The reference strains C1576 and J2315, for genomovar II and III, respectively, were included in the study. The bacteria were grown on solid media, the exopolysaccharides produced were purified, and their structures were determined. In addition, sugar analysis of sputum samples was accomplished to search for EPS produced in vivo. Results: Six strains out of seven produced the exopolysaccharide cepacian, while one strain of B. multivorans produced a completely different polymer, previously known in the literature as PS1. Two strains synthesised very small amounts of EPS. No definitive evidence for the presence of cepacian in sputum samples was found. Conclusions: Most strains examined produced abundant amounts of polysaccharides. Cepacian was the most common EPS isolated and its production was not associated to a particular genomovar

The political economy of digital profiteering: communication resource mobilization by anti-vaccination actors

Contemporary communication requires both a supply of content and a digital information infrastructure. Modern campaigns of misinformation are especially dependent on that back-end infrastructure for tracking and targeting a sympathetic audience and generating revenue that can sustain the campaign financially—if not enable profiteering. However, little is known about the political economy of misinformation, particularly those campaigns spreading misleading or harmful content about public health guidelines and vaccination programs. To understand the political economy of health misinformation, we analyze the content and infrastructure networks of 59 groups involved in communicating misinformation about vaccination programs. With a unique collection of tracker and communication infrastructure data, we demonstrate how the political economy of misinformation depends on platform monetization infrastructures. We offer a theory of communication resource mobilization that advances understanding of the communicative context, organizational interactions, and political outcomes of misinformation production

THE INHIBITION OF MYCOTOXINS BIOSYNTHESIS BY a-HETEROPOLYSACCHARIDES OF TRAMETES VERSICOLOR.

The contamination of food commodities by mycotoxins (aflatoxins, ochratoxin A, Fusarium toxins) which are health hazardous and carcinogenic secondary metabolites produced by different fungi (Aspergillus flavus, A. carbonarius, Fusarium verticillioides), has to be strictly controlled to safeguard human and animal health. Extant control methods are mainly based on chemical strategy (pesticides and fungicides). However, the use of substances synthesised by some basidiomycetes with a lower impact on the environment and on human health have produced encouraging results. Trametes versicolor is a basidiomycete known for its therapeutic effects mainly based on the production of several glycoproteins and exoglucans which display anti-tumoral action and anti-oxidative effects. The semi-purified exo-polysaccharides and glycoproteins secreted by this mushroom had previously shown the ability to inhibit the biosynthesis of different mycotoxins (aflatoxins, ochratoxin A, Fusarium toxins). In this study, the exo-polysaccharidic component secreted T. versicolor was purified by chromatographic separation techniques (Sephacryl S-300) and analysed by 1H- and 13C-NMR. Two-dimensional HSQC and COSY analysis have revealed the presence of highly complexed a-glucans with a mol. wt of ca. 50 kDa. We hypothesise that these fungal polysaccharides can act as non-self signals capable of modulating secondary metabolism in mycotoxigenic fungi. The results obtained are promising in view of the implementation of a more environment friendly strategy, so as to achieve a better control of different toxins that are often concomitantly present in foods and feeds