Surface Exposure and Packing of Lipoproteins into Outer Membrane Vesicles Are Coupled Processes in Bacteroides

Species from the Bacteroides genus are predominant members of the human gut microbiota. OMVs in Bacteroides have been shown to be important for the homeostasis of complex host-commensal relationships, mainly involving immune tolerance and protection from disease. OMVs carry many enzymatic activities involved in the cleavage of complex polysaccharides and have been proposed as public goods that can provide growth to other bacterial species by release of polysaccharide breakdown products into the gut lumen. This work shows that the presence of a negatively charged rich amino acid motif (LES) is required for efficient packing of the surface-exposed alpha-amylase SusG into OMVs. Our findings strongly suggest that surface exposure is coupled to packing of Bacteroides lipoproteins into OMVs. This is the first step in the generation of tailor-made probiotic interventions that can exploit LES-related sequences to generate Bacteroides strains displaying proteins of interest in OMVs.Outer membrane vesicles (OMVs) are spherical structures derived from the outer membranes (OMs) of Gram-negative bacteria. Bacteroides spp. are prominent components of the human gut microbiota, and OMVs produced by these species are proposed to play key roles in gut homeostasis. OMV biogenesis in Bacteroides is a poorly understood process. Here, we revisited the protein composition of Bacteroides thetaiotaomicron OMVs by mass spectrometry. We confirmed that OMVs produced by this organism contain large quantities of glycosidases and proteases, with most of them being lipoproteins. We found that most of these OMV-enriched lipoproteins are encoded by polysaccharide utilization loci (PULs), such as the sus operon. We examined the subcellular locations of the components of the Sus system and found a split localization; the alpha-amylase SusG is highly enriched in OMVs, while the oligosaccharide importer SusC remains mostly in the OM. We found that all OMV-enriched lipoproteins possess a lipoprotein export sequence (LES), and we show that this signal mediates translocation of SusG from the periplasmic face of the OM toward the extracellular milieu. Mutations in the LES motif caused defects in surface exposure and recruitment of SusG into OMVs. These experiments link, for the first time, surface exposure to recruitment of proteins into OMVs. We also show that surface-exposed SusG in OMVs is active and rescues the growth of bacterial cells incapable of growing on starch as the only carbon source. Our results support the role of OMVs as “public goods” that can be utilized by other organisms with different metabolic capabilities

Exploiting the Properties of Ti-Doped CVD-Grown Diamonds for the Assembling of Electrodes

A hybrid chemical vapor deposition (CVD)‐powder flowing technique specifically developed in lab has been employed to produce high‐quality polycrystalline diamond layers containing Ti inclusions. Morphology, structural features, and surface composition of nanocomposite diamond‐based samples produced by different growth times have been analyzed by scanning electron microscopy, Raman and Auger spectroscopy, respectively. The CVD methodology adopted for the Ti incorporation in the diamond lattice does not perturb the crystalline quality of the diamond matrix, therefore maintaining the outstanding properties of the C‐sp3 phase. The functional properties of the nanocomposite layers have been tested by nanoindentation and I–V measurements. The electrochemical performance of the diamond/Ti electrodes is evaluated by performing cyclic voltammetry in different media, namely, acidic, neutral, and basic aqueous solutions, and by estimating the rate constant of heterogeneous electron transfer to diamond surface for the ferro/ferricyanide redox couple. The rather good electrochemical performances, the mechanical strength, and the chemical inertness of the Ti‐doped diamond electrodes produced by the CVD approach, comply with the whole set of technological requirements, such as robustness, long durability, and biocompatibility, required for use in hostile environments or in biological systems

Underdiagnosis and undertreatment of migraine in Italy: a survey of patients attending for the first time 10 headache centres.

The aim of this study was to asses the clinical features, pattern of healthcare and drug utilization of migraine patients attending 10 Italian headache centres (HC). Migraine is underdiagnosed and undertreated everywhere throughout the world, despite its considerable burden. Migraine sufferers often deal with their problem alone using self-prescribing drugs, whereas triptans are used by a small proportion of patients. All patients attending for the first time 10 Italian HCs over a 3-month period were screened for migraine. Migraine patients underwent a structured direct interview about previous migraine diagnosis, comorbidity, headache treatments and their side-effects and healthcare utilization for migraine. Patient satisfaction with their usual therapy for the migraine attack was evaluated with the Migraine-Assessment of Current Therapy (ACT) questionnaire. The quality of life of migraine patients was assessed by mean of Short Form (SF)-12 and Migraine-Specific Quality of life (MSQ) version 2.1 questionnaires. Of the 2675 patients who attended HCs for the first time during the study period, 71% received a diagnosis of migraine and the first 953 subjects completed the study out of 1025 patients enrolled. Only 26.8% of migraine patients had a previous diagnosis of migraine; 62.4% of them visited their general practitioner (GP) in the last year, 38.2% saw a specialist for headache, 23% attended an Emergency Department and 4.5% were admitted to hospital for migraine; 82.8% of patients used non-specific drugs for migraine attacks, whereas 17.2% used triptans and only 4.8% used a preventive migraine medication. Triptans were used by 46.4% of patients with a previous diagnosis of migraine. About 80% of migraine patients took over-the-counter medications. The Migraine-ACT revealed that 60% of patients needed a change in their treatment of migraine attacks, 85% of whom took non-specific drugs. Both the MSQ version 2.1 and the SF-12 questionnaires indicated a poor quality of life of most patients. Migraine represents the prevalent headache diagnosis in Italian HCs. Migraine is still underdiagnosed in Italy and migraine patients receive a suboptimal medical approach in our country, despite the healthcare utilization of migraine subjects being noteworthy. A cooperative network involving GPs, neurologists and headache specialists is strongly desirable in order to improve long-term migraine management in Italy. © 2009 Blackwell Publishing Ltd

Polysaccharide degradation by the Bacteroidetes: mechanisms and nomenclature

The Bacteroidetes phylum is renowned for its ability to degrade a wide range of complex carbohydrates, a trait that has enabled its dominance in many diverse environments. The best studied species inhabit the human gut microbiome and use polysaccharide utilization loci (PULs), discrete genetic structures that encode proteins involved in the sensing, binding, deconstruction, and import of target glycans. In many environmental species, polysaccharide degradation is tightly coupled to the phylum-exclusive type IX secretion system (T9SS), which is used for the secretion of certain enzymes and is linked to gliding motility. In addition, within specific species these two adaptive systems (PULs and T9SS) are intertwined, with PUL-encoded enzymes being secreted by the T9SS. Here, we discuss the most noteworthy PUL and non-PUL mechanisms that confer specific and rapid polysaccharide degradation capabilities to the Bacteroidetes in a range of environments. We also acknowledge that the literature showcasing examples of PULs is rapidly expanding and developing a set of assumptions that can be hard to track back to original findings. Therefore, we present a simple universal description of conserved PUL functions and how they are determined, while proposing a common nomenclature describing PULs and their components, to simplify discussion and understanding of PUL systems

Molecular basis of lipid-linked oligosaccharide recognition and processing by bacterial oligosaccharyltransferase

ISSN:1545-9993ISSN:1545-998