Desulfovibrio desulfuricans isolates from the gut of a single individual: Structural and biological lipid A characterization

AbstractThe levels of sulfate-reducing bacteria (SRB), including Desulfovibrionaceae, in the gut increase following a fat-enriched diet. Endotoxins from gut microbiota contribute to the inflammation process, leading to metabolic diseases. Thus, we sought to characterize the lipid A structures of Desulfovibrionaceae lipopolysaccharides (LPS) that are associated with the microbiota inflammatory properties. LPS variants were obtained from two SRB isolates from the gut of a single individual. These LPS variants shared similar lipid A moieties with Enterobacterial LPS, but differed from one another with regard to fatty-acid numbers and endotoxic activity. This first complete structural characterization of Desulfovibrio lipid A gives new insights into previously published data on Desulfovibrio lipid A biosynthesis. LPS microdiversity within SRBs illustrates how adaptation can influence pro-inflammatory potential

Processamento auditivo em crianças e adolescentes em situação de risco e vulnerabilidade

CONTEXT AND OBJECTIVE: Children and adolescents who live in situations of social vulnerability present a series of health problems. Nonetheless, affirmations that sensory and cognitive abnormalities are present are a matter of controversy. The aim of this study was to investigate aspects to auditory processing, through applying the brainstem auditory evoked potential (BAEP) and behavioral auditory processing tests to children living on the streets, and comparison with a control group. DESIGN AND SETTING: Cross-sectional study in the Laboratory of Auditory Processing, School of Medicine, Universidade de São Paulo. METHODS: The auditory processing tests were applied to a group of 27 individuals, subdivided into 11 children (7 to 10 years old) and 16 adolescents (11 to 16 years old), of both sexes, in situations of social vulnerability, compared with an age-matched control group of 10 children and 11 adolescents without complaints. The BAEP test was also applied to investigate the integrity of the auditory pathway. RESULTS: For both children and adolescents, there were significant differences between the study and control groups in most of the tests applied, with significantly worse performance in the study group, except in the pediatric speech intelligibility test. Only one child had an abnormal result in the BAEP test. CONCLUSIONS: The results showed that the study group (children and adolescents) presented poor performance in the behavioral auditory processing tests, despite their unaltered auditory brainstem pathways, as shown by their normal results in the BAEP test

The Drosophila immune system detects bacteria through specific peptidoglycan recognition

The Drosophila immune system discriminates between different classes of infectious microbes and responds with pathogen-specific defense reactions through selective activation of the Toll and the immune deficiency (Imd) signaling pathways. The Toll pathway mediates most defenses against Gram-positive bacteria and fungi, whereas the Imd pathway is required to resist infection by Gram-negative bacteria. The bacterial components recognized by these pathways remain to be defined. Here we report that Gram-negative diaminopimelic acid-type peptidoglycan is the most potent inducer of the Imd pathway and that the Toll pathway is predominantly activated by Gram-positive lysine-type peptidoglycan. Thus, the ability of Drosophila to discriminate between Gram-positive and Gram-negative bacteria relies on the recognition of specific forms of peptidoglycan

Lipopolysaccharides: structure, function and bacterial identifications

Lipopolysaccharides (LPS) are the main components of the outer membrane of Gram-negative bacteria. They are glycolipids containing a lipid moiety called lipid A, more often made of a bis-phosphorylated glucosamine disaccharide, carrying fatty acids in ester and amide linkages. Lipid A is linked to a core oligosaccharide of about 10 sugars, substituted in the wild-type strains, by long-chain oligosaccharide repetitive units, extending outside the bacteria and representing their main antigens. In addition to determine the serotype of the bacterium, LPS are highly potent biological molecules, capable of eliciting at the level of minute amounts, beneficial, as well as deleterious activities

Etude de l'effet de la salinité sur la survie et le pouvoir infectieux de Rhizobia Nodulant les Acacias : Analyse de la structure des lipopolysaccharides

LE KREMLIN-B.- PARIS 11-BU Méd (940432101) / SudocSudocFranceF

Structure of the Bordetella trematum LPS O-chain subuit

NRC publication: Ye

A comparative study of the complete lipopolysaccharide structures and biosynthesis loci of Bordetella avium, B. hinzii, and B. trematum

International audienceA dozen species of human and animal pathogens have been described to date in the Bordetella genus, with the majority being respiratory tract pathogens. Bordetella avium lipopolysaccharides have been shown to be important virulence factors for this bird pathogen. B. hinzii is closely related to the B. avium species, but has also been isolated from humans. B. trematum is associated to ear and blood infections in humans. Its lipid A structure, the biological active moiety of LPS, was found to be closely related to those of B. avium and B. hinzii. It is important to unveil the subtle structural modifications orchestrated during the LPS biosynthetic pathway to better understand host adaptation. The present data are also important in the context of deciphering the virulence pathways of this important genus containing the major pathogens B. pertussis and B. parapertussis, responsible for whooping cough. We recently reported the isolated lipid A structures of the three presented species, following the previously identified O-chain structures. In the present study, we provide details on the free and O-chain-linked core oligosaccharides which were required to characterize the complete LPS structures. Data are presented here in relation to relevant biosynthesis genes. The present characterization of the three species is well illustrated by Matrix Assisted Laser Desorption Mass Spectrometry experiments, and data were obtained mainly on native LPS molecules for the first time. (C) 2018 Elsevier B.V. and Societe Francaise de Biochimie et Biologie Moleculaire (SFBBM). All rights reserved

Micromethods for Isolation and Structural Characterization of Lipid A, and Polysaccharide Regions of Bacterial Lipopolysaccharides

Lipopolysaccharides (LPS) are major components of the external membrane of most Gram-negative bacteria, providing them with an effective permeability barrier. They are essentially composed of a hydrophilic polysaccharide region (PS) linked to a hydrophobic one, termed lipid A. The LPS polysaccharide moiety is divided into the core oligosaccharide (OS) and O-chain repetitive elements. Depending on their individual variable fine structures, LPS may be potent immunomodulators. The lipid A structure is a key determinant for LPS activity. However, the presence of the core region, or at least of the highly charged 3-deoxy-d-manno-oct-2-ulosonic acid molecules, is also important for preserving the native lipid A conformation within individual LPS molecules. We describe herein four rapid and practical micromethods for LPS, lipid A, and core OS structural analyses. The first method allows the direct isolation of lipid A from whole bacteria cell mass; the second describes conditions for the sequential release of fatty acids enabling the characterization of their substitution position in the lipid A backbone, to be determined by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The third one is a microscale procedure for the mass spectra screening of LPS, lipid A, and PS using triethylamine and citric acid. The fourth method is a chromatography procedure for Rough-type LPS on thin-layer-chromatography. These methods were developed to be coupled to mass-spectrometry (e.g., MALDI-MS) but can also be used with other analytical techniques (e.g., chromatography). Examples are given with reference to two major human pathogens: Bordetella pertussis and Pseudomonas aeruginosa; to one porcine pathogen: Actinobacillus pleuropneumoniae; and to commercial samples of Salmonella Minnesota Re595 LPS

Antimicrobial Peptide Resistance Genes in the Plant Pathogen Dickeya dadantii

International audienceModification of teichoic acid through the incorporation of D-alanine confers resistance in Gram-positive bacteria to antimicro-bial peptides (AMPs). This process involves the products of the dltXABCD genes. These genes are widespread in Gram-positive bacteria, and they are also found in a few Gram-negative bacteria. Notably, these genes are present in all soft-rot enterobacteria (Pectobacterium and Dickeya) whose dltDXBAC operons have been sequenced. We studied the function and regulation of these genes in Dickeya dadantii. dltB expression was induced in the presence of the AMP polymyxin. It was not regulated by PhoP, which controls the expression of some genes involved in AMP resistance, but was regulated by ArcA, which has been identified as an activator of genes involved in AMP resistance. However, arcA was not the regulator responsible for polymyxin induction of these genes in this bacterium, which underlines the complexity of the mechanisms controlling AMP resistance in D. dadantii. Two other genes involved in resistance to AMPs have also been characterized, phoS and phoH. dltB, phoS, phoH, and arcA but not dltD mutants were more sensitive to polymyxin than the wild-type strain. Decreased fitness of the dltB, phoS, and phoH mutants in chicory leaves indicates that their products are important for resistance to plant AMP

Fine structure analysis of lipopolysaccharides in bacteriophage-resistant Pseudomonas aeruginosa PAO1 mutants

Pseudomonas aeruginosa lipopolysaccharides (LPS) serve as primary receptors for many bacteriophages and, consequently, their biosynthesis is frequently affected in phage-resistant mutants. We previously isolated phage-resistant PAO1 mutants using three different phages, and showed that they were affected in the synthesis of LPS. Here we have investigated in detail the effect of mutations in seven genes involved in different steps of the production of core and oligosaccharide chains. The band profile of purified LPS was analysed by PAGE, and we further characterized the O-chains and core structures by MALDI mass spectrometry (MS). Mild LPS extraction conditions and native LPS MS analyses helped unveil lipid A molecular species with three phosphate residues in the close vicinity of the already highly charged inner-core region. No other MS direct analysis has allowed this peculiarity to be demonstrated for native lipid A high-molecular-weight molecular species, in normal growth conditions and without involving separation techniques. The present results shed light on the possible interactions between the phages and the LPS structures in the early phase of infection