Contribution of plasmid-encoded peptidase S8 (PrtP) to adhesion and transit in the gut of Lactococcus lactis IBB477 strain

The ability of Lactococcus lactis to adhere to the intestinal mucosa can potentially prolong the contact with the host, and therefore favour its persistence in the gut. In the present study, the contribution of plasmid-encoded factors to the adhesive and transit properties of the L. lactis subsp. cremoris IBB477 strain was investigated. Plasmid-cured derivatives as well as deletion mutants were obtained and analysed. Adhesion tests were performed using non-coated polystyrene plates, plates coated with mucin or fibronectin and mucus-secreting HT29-MTX intestinal epithelial cells. The results indicate that two plasmids, pIBB477a and b, are involved in adhesion of the IBB477 strain. One of the genes localised on plasmid pIBB477b (AJ89_14230), which encodes cell wall-associated peptidase S8 (PrtP), mediates adhesion of the IBB477 strain to bare, mucin- and fibronectincoated polystyrene, as well as to HT29-MTX cells. Interactions between bacteria and mucus secreted by HT29- MTX cells were further investigated by fluorescent staining and confocal microscopy. Confocal images showed that IBB477 forms dense clusters embedded in secreted mucus. Finally, the ability of IBB477 strain and its ΔprtP deletion mutant to colonise the gastrointestinal tract of conventional C57Bl/6mice was determined. Both strains were present in the gut for up to 72 h. In summary, adhesion and persistence of IBB477 were analysed by in vitro and in vivo approaches, respectively. Our studies revealed that plasmidic genes encoding cell surface proteins are more involved in the adhesion of IBB477 strain than in the ability to confer a selective advantage in the gut

Evaluation of serum extracellular vesicle isolation methods for profiling miRNAs by next-generation sequencing

Extracellular vesicles (EVs) are intercellular communicators with key functions in physiological and pathological processes and have recently garnered interest because of their diagnostic and therapeutic potential. The past decade has brought about the development and commercialization of a wide array of methods to isolate EVs from serum. Which subpopulations of EVs are captured strongly depends on the isolation method, which in turn determines how suitable resulting samples are for various downstream applications. To help clinicians and scientists choose the most appropriate approach for their experiments, isolation methods need to be comparatively characterized. Few attempts have been made to comprehensively analyse vesicular microRNAs (miRNAs) in patient biofluids for biomarker studies. To address this discrepancy, we set out to benchmark the performance of several isolation principles for serum EVs in healthy individuals and critically ill patients. Here, we compared five different methods of EV isolation in combination with two RNA extraction methods regarding their suitability for biomarker discovery-focused miRNA sequencing as well as biological characteristics of captured vesicles. Our findings reveal striking method-specific differences in both the properties of isolated vesicles and the ability of associated miRNAs to serve in biomarker research. While isolation by precipitation and membrane affinity was highly suitable for miRNA-based biomarker discovery, methods based on size-exclusion chromatography failed to separate patients from healthy volunteers. Isolated vesicles differed in size, quantity, purity and composition, indicating that each method captured distinctive populations of EVs as well as additional contaminants. Even though the focus of this work was on transcriptomic profiling of EV-miRNAs, our insights also apply to additional areas of research. We provide guidance for navigating the multitude of EV isolation methods available today and help researchers and clinicians make an informed choice about which strategy to use for experiments involving critically ill patients

The dynamic architecture of the metabolic switch in Streptomyces coelicolor

[EN] Background: During the lifetime of a fermenter culture, the soil bacterium S. coelicolor undergoes a major metabolic switch from exponential growth to antibiotic production. We have studied gene expression patterns during this switch, using a specifically designed Affymetrix genechip and a high-resolution time-series of fermenter-grown samples.Results: Surprisingly, we find that the metabolic switch actually consists of multiple finely orchestrated switching events. Strongly coherent clusters of genes show drastic changes in gene expression already many hours before the classically defined transition phase where the switch from primary to secondary metabolism was expected. The main switch in gene expression takes only 2 hours, and changes in antibiotic biosynthesis genes are delayed relative to the metabolic rearrangements. Furthermore, global variation in morphogenesis genes indicates an involvement of cell differentiation pathways in the decision phase leading up to the commitment to antibiotic biosynthesis.Conclusions: Our study provides the first detailed insights into the complex sequence of early regulatory events during and preceding the major metabolic switch in S. coelicolor, which will form the starting point for future attempts at engineering antibiotic production in a biotechnological settingSIWe are very grateful to Mervyn Bibb for his generous support with the Affymetrix custom microarray design. We acknowledge the excellent technical help of K. Klein, S. Poths, M. Walter, A. Øverby and E. Hansen. This project was supported by grants of the ERA-NET SySMO Project [GEN2006-27745-E/SYS]: (P-UK-01-11-3i) and the Research Council of Norway [project no. 181840/I30

Stainless Steel Substrate Pretreatment Effects on Copper Nucleation and Stripping during Copper Electrowinning

Abstract: The effects of surface pretreatment of 304 stainless steel (SS) substrates on copper film formation, adhesion, and purity obtained by galvanostatic electrodeposition at a current density of – 30 mA cm−2 are presented. The polished substrate produced more copper nuclei, resulting in an increase of the adhesion as compared to chemically oxidized SS substrate. The adhesion of the copper deposits was characterized by a Nano-scratch tester (NST). The nucleation behavior is associated with the flatband potential of the SS surface, which was derived from capacitance measurements. The grain size of copper deposits was characterized by field emission scanning electron microscopy (FESEM). Copper grains were smaller on the polished SS with a size of less than 1 µm after 5 min of electrodeposition. High-purity copper deposits with \u3c 1 ppm S (detection limit) were obtained on the oxidized SS substrate compared to 2.5 ppm for the polished SS substrate. Atomic force microscopy (AFM) measurements showed that the copper deposits were 25% less rough on the polished SS as compared to the oxidized SS. The results indicate that the obtained purity of the copper deposit relates to the grain size of the deposit, rather than the initial surface roughness. In the context of industrial electrowinning, high adherence to the polished substrate could increase the operation time of the copper cathode stripping. Hence for electrowinning from copper sulfate electrolytes, oxidizing the SS surface prior to deposition could lead to higher purity along with enhanced stripping

Croissance et morphologie des jeunes pins sylvestres en reponse a la lumiere sous couvert forestier

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Effect of speciation and composition on the kinetics and precipitation of arsenic sulfide from industrial metallurgical wastewater

Precipitation of arsenic as As2S3 produces little waste sludge, has the potential for low chemical consumption and for selective metal(loid) removal. In this study, arsenic removal from acidic (pH 2), metallurgical wastewater was tested in industrially relevant conditions. Sulfides added at a S:As molar ratio of 2.5 and 5 resulted in removal of 99% and 84% of As(III) and As(V). Precipitation of As2S3 from the As(III) and industrial wastewater containing 17% As(V) was nearly instantaneous. For the synthetic As(V) solution, reduction to As(III) was the rate limiting step. At a S:As ratio of 20 and an observed removal rate (k2 = 4.8 (mol L−1) h−1), two hours were required to remove of 93% of arsenic from a 1 g As L−1 solution. In the case of As(V) in industrial samples this time lag was not observed, showing that components in the industrial wastewater affected the removal and reduction of arsenate. Speciation also affected flocculation and coagulation characteristics of As2S3 particles: As(V) reduction resulted in poor coagulation and flocculation. Selective precipitation of arsenic was possible, but depended on speciation, S:As ratio and other metals present

Electrochemical codeposition of copper-antimony and interactions with electrolyte additives : towards the use of electronic waste for sustainable copper electrometallurgy

The use of electronic waste or low grade materials as feedstock for the electrolytic production of copper is challenging because impurity metals such as Sb(III) are introduced in the electrolyte. In this work, the mechanisms that lead to antimony contamination in electrolytic copper are studied. Linear sweep voltammetry experiments indicate that the reduction of Sb(III) is kinetically slow in the absence of Cu(II). In the presence of Cu (II), however, reduction of Sb(III) can occur readily by the codeposition of Cu(II) and Sb(III) as demonstrated by chronoamperometry. The ToF-SIMS analyses confirmed the codeposition of antimony in the very first micrometer of the copper deposit, enabled by the nucleation overpotential for galvanostatic copper electrodeposition under conditions relevant for the commercial production of copper. Based on potentiostatic electrodeposition experiments, we suggest that a copper concentration of >40 g L-1 Cu(II) in Sb(III) containing electrolytes is beneficial to obtain high purity copper. Codeposition reactions were impacted by the presence of additives (thiourea, glue and chloride ions). In particular, the addition of 0.02 g L-1 chloride mitigated the codeposition of antimony (0.02 g L-1 Sb(III)) to produce grade A copper. For optimal removal of Sb(III) from bleed electrolytes, a molar ratio of ~3 Cu(II)/Sb(III) should be maintained (e.g. 0.3 g L-1 Cu(II) for a typical concentration of 0.2 g L-1 Sb(III))