Bioleaching to reprocess sulfidic polymetallic primary mining residues: Determination of metal leaching mechanisms

This is the final version. Available on open access from Elsevier via the DOI in this recordThe mining of non-ferrous metals produces the largest volume of metal-containing, extractive waste in Europe, and about 29% of all the waste produced in the EU-28. In the framework of the European project NEMO (Near-zero-waste recycling of low-grade sulfidic mining waste for critical-metal, mineral and construction raw-material production in a circular economy), new ways to valorize sulfidic tailings are being developed through the recovery of valuable metals and critical raw materials and the transformation of the residual in clean mineral fraction to be used for the mass production of cement, concrete and construction products. The first step of the NEMO concept consists of removing the sulfides remaining from primary bioleaching and extracting the metals in the residual material (known as ‘secondary ore’) using either enhanced bioleaching or an alkaline autoclave conversion processes. This paper focuses on one of the project case studies, the secondary ore, obtained from an operating heap leaching plant (Terrafame, Finland). This material still contains several sulfide minerals (pyrrhotite, pyrite, sphalerite, pentlandite, violarite, chalcopyrite) and significant amounts of metals (Zn, Ni, Cu, Co, rare earth elements). The study aimed to characterize the mineralogy of the secondary ore and perform bioleaching in 2 L-stirred tank reactors, with three microbial cultures growing at 42, 48 and 55 °C. These results were compared to abiotic experiments, performed under the same conditions. Nickel was released very quickly, suggesting that part of Ni dissolved in the primary heap was re-precipitated and remained in the secondary ore. By contrast, Cu dissolution was much slower but the kinetics were substantially improved when the temperature was increased to 55 °C. Cobalt dissolution kinetics were highly improved by the bacterial activity, whatever the consortium. This is consistent with the presence of Co in the pyrite in the secondary ore.European Union Horizon 202

Variability in energy cost of running at the end of a triathlon and a marathon

International audienceThe aim of this study was to investigate the increase in energy cost of running occurring at the end of a triathlon and a marathon event and to link them to the metabolic and hormonal changes, as well as to variations in stride length. Seven subjects took part in 3 experimental situations: a 2 h 15 min triathlon (30 min swimming, 60 min cycling and 45 min running), a 2 h 15 min marathon (MR) were the fast 45 min were run at the same speed as the triathlon run (TR), and a 45 min isolated run (IR) done at triathlon speed. The results show that energy cost during MR was higher than during TR (p < 0.01) (+ 8.9 %). Similar observations were made for pulmonary ventilation (+ 7.9 %) and heart rate (+ 6.3 %). Moreover, the values were significantly greater than the values obtained during the IR. TR and MR lead to greater weight loss (p < 0.01) (2.4±0.3 kg) than IR (1 ± 0.2 kg). The triathlon and the marathon produced a large decrease in plasma volume (respectively 19.6 ± 1.4 % and 12.9 ± 1.1 %) compared to IR (2 ± 0.4 %). Plasma renin activity was higher for the triathlon and the marathon than for the IR (p < 0.01). MR produces a significantly greater increase in plasma free fatty acids (F.F.A.) than TR (p < 0.05) and IR (p < 0.01). In addition, the F.F.A. at the end of TR were significantly higher than IR (p < 0.05). At the end of the trial the mean stride lengths for TR and IR were greater (+ 15 %) (p <0.01) than for MR. This study, carried out with subjects running overground, confirms the decrease in running efficiency previously shown at the end of a laboratory triathlon, and demonstrates that this decrease is lower than that occurring during a marathon

Structure, rheology, and copper-complexation of a hyaluronan-like exopolysaccharide from Vibrio

MO245 exopolysaccharide (EPS) was produced in laboratory conditions from Vibrio genus microorganism isolated from bacterial mats found in Moorea Island. Its structure consists of a linear tetrasaccharide repeating unit →4)-β-D-GlcpA-(1→4)-α-D-GalpNAc-(1→3)-β-D-GlcpNAc-(1→4)-β-D-GlcpA-(1→ containing covalently-linked 5% of glucose, galactose, and rhamnose, determined by methylation analyses and NMR spectroscopy. The molecular weight, radius of gyration (Rg) and intrinsic viscosity, [η], determined by gel permeation chromatography with light scattering and viscosity detection, were 513 ± 4 kDa (PDI, 1.42 ± 0.01), 6.7 ± 0.3 dl/g and 56 ± 0.3 nm respectively. The chelation of the EPS with copper divalent ions leads to the instantaneous formation of gels. The structural similitude proposed, based in an equal ratio of GlcA to N-acetylated sugars and in the same type of glyosidic linkages present in the repeating unit (alternated 1→3 and 1→4 linkages), is translated into analogous physicochemical properties: MO245 EPS is a flexible polyelectrolyte, with scaling exponents similar to that described for HA. This similitude opens opportunities in future drug delivery, tissue engineering, and cosmetic applications.publishe

Proteins that bind methylated DNA and human cancer: reading the wrong words

DNA methylation and the machinery involved in epigenetic regulation are key elements in the maintenance of cellular homeostasis. Epigenetic mechanisms are involved in embryonic development and the establishment of tissue-specific expression, X-chromosome inactivation and imprinting patterns, and maintenance of chromosome stability. The balance between all the enzymes and factors involved in DNA methylation and its interpretation by different groups of nuclear factors is crucial for normal cell behaviour. In cancer and other diseases, misregulation of epigenetic marks is a common feature, also including DNA methylation and histone post-translational modifications. In this scenario, it is worth mentioning a family of proteins characterized by the presence of a methyl-CpG-binding domain (MBDs) that are involved in interpreting the information encoded by DNA methylation and the recruitment of the enzymes responsible for establishing a silenced state of the chromatin. The generation of novel aberrantly hypermethylated regions during cancer development and progression makes MBD proteins interesting targets for their biological and clinical implications

Stress-Induced PARP Activation Mediates Recruitment of Drosophila Mi-2 to Promote Heat Shock Gene Expression

Eukaryotic cells respond to genomic and environmental stresses, such as DNA damage and heat shock (HS), with the synthesis of poly-[ADP-ribose] (PAR) at specific chromatin regions, such as DNA breaks or HS genes, by PAR polymerases (PARP). Little is known about the role of this modification during cellular stress responses. We show here that the nucleosome remodeler dMi-2 is recruited to active HS genes in a PARP–dependent manner. dMi-2 binds PAR suggesting that this physical interaction is important for recruitment. Indeed, a dMi-2 mutant unable to bind PAR does not localise to active HS loci in vivo. We have identified several dMi-2 regions which bind PAR independently in vitro, including the chromodomains and regions near the N-terminus containing motifs rich in K and R residues. Moreover, upon HS gene activation, dMi-2 associates with nascent HS gene transcripts, and its catalytic activity is required for efficient transcription and co-transcriptional RNA processing. RNA and PAR compete for dMi-2 binding in vitro, suggesting a two step process for dMi-2 association with active HS genes: initial recruitment to the locus via PAR interaction, followed by binding to nascent RNA transcripts. We suggest that stress-induced chromatin PARylation serves to rapidly attract factors that are required for an efficient and timely transcriptional response

Application of machine learning methods to histone methylation ChIP-Seq data reveals H4R3me2 globally represses gene expression

<p>Abstract</p> <p>Background</p> <p>In the last decade, biochemical studies have revealed that epigenetic modifications including histone modifications, histone variants and DNA methylation form a complex network that regulate the state of chromatin and processes that depend on it including transcription and DNA replication. Currently, a large number of these epigenetic modifications are being mapped in a variety of cell lines at different stages of development using high throughput sequencing by members of the ENCODE consortium, the NIH Roadmap Epigenomics Program and the Human Epigenome Project. An extremely promising and underexplored area of research is the application of machine learning methods, which are designed to construct predictive network models, to these large-scale epigenomic data sets.</p> <p>Results</p> <p>Using a ChIP-Seq data set of 20 histone lysine and arginine methylations and histone variant H2A.Z in human CD4⁺T-cells, we built predictive models of gene expression as a function of histone modification/variant levels using Multilinear (ML) Regression and Multivariate Adaptive Regression Splines (MARS). Along with extensive crosstalk among the 20 histone methylations, we found H4R3me2 was the most and second most globally repressive histone methylation among the 20 studied in the ML and MARS models, respectively. In support of our finding, a number of experimental studies show that PRMT5-catalyzed symmetric dimethylation of H4R3 is associated with repression of gene expression. This includes a recent study, which demonstrated that H4R3me2 is required for DNMT3A-mediated DNA methylation--a known global repressor of gene expression.</p> <p>Conclusion</p> <p>In stark contrast to univariate analysis of the relationship between H4R3me2 and gene expression levels, our study showed that the regulatory role of some modifications like H4R3me2 is masked by confounding variables, but can be elucidated by multivariate/systems-level approaches.</p