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1.
Application of co-composted biochar significantly improved plant-growth relevant physical/chemical properties of a metal contaminated soil.
Teodoro, M, Trakal, L, Gallagher, BN, Šimek, P, Soudek, P, Pohořelý, M, Beesley, L, Jačka, L, Kovář, M, Seyedsadr, S, et al
Chemosphere. 2020;:125255
Abstract
A woody-biochar was added to waste biomass during a composting process. The resulting compost-char was amended to a metal contaminated soil and two plant species, L. perenne and E. sativa, were grown in a pot experiment to determine 1) plant survival and stress factors, 2) uptake of metals to plants and, 3) chemical characteristics of sampled soils and pore waters. Compost supplemented with biochar after the composting process were also tested, as well as a commercially available compost, for comparison. Co-composting with biochar hastened the composting process, resulting in a composite material of reduced odour, increased maturity, circum-neutral pH and increased moisture retention than compost (increase by 3% of easily removable water content). When amended to the soil, CaCl2 extractable and pore water metals s were reduced by all compost treatments with little influence of biochar addition at any tested dose. Plant growth success was promoted furthest by the addition of co-composted biochar to the test soil, especially in the case of E. sativa. For both tested plant species significant reductions in plant metal concentrations (e.g. 8-times for Zn) were achieved, against the control soil, by compost, regardless of biochar addition. The results of this study demonstrate that the addition of biochar into the composting process can hasten the stability of the resulting compost-char, with more favourable characteristics as a soil amendment/improver than compost alone. This appears achievable whilst also maintaining the provision of available nutrients to soils and the reduction of metal mobility, and improved conditions for plant establishment.
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2.
Comparing Nonbonded Metal Ion Models in the Divalent Cation Binding Protein PsaA.
MacDermott-Opeskin, H, McDevitt, CA, O'Mara, ML
Journal of chemical theory and computation. 2020;(3):1913-1923
Abstract
Divalent metal cations are essential for many biological processes; however, accurately modeling divalent metal ions has proved a significant challenge for molecular dynamics force fields. Here we show that the choice of ion model influences the observed dynamics in PsaA, a metal binding protein from Streptococcus pneumoniae. We conduct extensive unbiased simulations and free energy calculations of PsaA bound to its cognate ligand Mn2+ and inhibitory ligand Zn2+ using three nonbonded ion models: a 12-6 model, a 12-6-4 model, and a multisite model. The observed coordination geometries and metal binding dynamics are sensitive to the choice of ion model, with the most dramatic differences observed in free energy calculations of ion release. We show that the conformational ensemble of Mn-bound PsaA is more similar to the crystallographic metal bound open state. This work extends the current model of PsaA metal binding and provides a framework for the rationalization of experimentally determined metal binding behavior. Our findings support the use of the 12-6-4 ion model for further simulations of divalent cation binding proteins.
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3.
Biological Factors, Metals, and Biomaterials Regulating Osteogenesis through Autophagy.
di Giacomo, V, Cataldi, A, Sancilio, S
International journal of molecular sciences. 2020;(8)
Abstract
Bone loss raises great concern in numerous situations, such as ageing and many diseases and in both orthopedic and dentistry fields of application, with an extensive impact on health care. Therefore, it is crucial to understand the mechanisms and the determinants that can regulate osteogenesis and ensure bone balance. Autophagy is a well conserved lysosomal degradation pathway, which is known to be highly active during differentiation and development. This review provides a revision of the literature on all the exogen factors that can modulate osteogenesis through autophagy regulation. Metal ion exposition, mechanical stimuli, and biological factors, including hormones, nutrients, and metabolic conditions, were taken into consideration for their ability to tune osteogenic differentiation through autophagy. In addition, an exhaustive overview of biomaterials, both for orthopedic and dentistry applications, enhancing osteogenesis by modulation of the autophagic process is provided as well. Already investigated conditions regulating bone regeneration via autophagy need to be better understood for finely tailoring innovative therapeutic treatments and designing novel biomaterials.
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4.
Allosteric control of metal-responsive transcriptional regulators in bacteria.
Baksh, KA, Zamble, DB
The Journal of biological chemistry. 2020;(6):1673-1684
Abstract
Many transition metals are essential trace nutrients for living organisms, but they are also cytotoxic in high concentrations. Bacteria maintain the delicate balance between metal starvation and toxicity through a complex network of metal homeostasis pathways. These systems are coordinated by the activities of metal-responsive transcription factors-also known as metal-sensor proteins or metalloregulators-that are tuned to sense the bioavailability of specific metals in the cell in order to regulate the expression of genes encoding proteins that contribute to metal homeostasis. Metal binding to a metalloregulator allosterically influences its ability to bind specific DNA sequences through a variety of intricate mechanisms that lie on a continuum between large conformational changes and subtle changes in internal dynamics. This review summarizes recent advances in our understanding of how metal sensor proteins respond to intracellular metal concentrations. In particular, we highlight the allosteric mechanisms used for metal-responsive regulation of several prokaryotic single-component metalloregulators, and we briefly discuss current open questions of how metalloregulators function in bacterial cells. Understanding the regulation and function of metal-responsive transcription factors is a fundamental aspect of metallobiochemistry and is important for gaining insights into bacterial growth and virulence.
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5.
Harnessing Metal Homeostasis Offers Novel and Promising Targets Against Candida albicans.
Hameed, S, Hans, S, Singh, S, Fatima, Z
Current drug discovery technologies. 2020;(4):415-429
Abstract
Fungal infections, particularly of Candida species, which are the commensal organisms of human, are one of the major debilitating diseases in immunocompromised patients. The limited number of antifungal drugs available to treat Candida infections, with the concomitant increasing incidence of multidrug-resistant (MDR) strains, further worsens the therapeutic options. Thus, there is an urgent need for the better understanding of MDR mechanisms, and their reversal, by employing new strategies to increase the efficacy and safety profiles of currently used therapies against the most prevalent human fungal pathogen, Candida albicans. Micronutrient availability during C. albicans infection is regarded as a critical factor that influences the progression and magnitude of the disease. Intracellular pathogens colonize a variety of anatomical locations that are likely to be scarce in micronutrients, as a defense strategy adopted by the host, known as nutritional immunity. Indispensable critical micronutrients are required both by the host and by C. albicans, especially as a cofactor in important metabolic functions. Since these micronutrients are not freely available, C. albicans need to exploit host reservoirs to adapt within the host for survival. The ability of pathogenic organisms, including C. albicans, to sense and adapt to limited micronutrients in the hostile environment is essential for survival and confers the basis of its success as a pathogen. This review describes that micronutrients availability to C. albicans is a key attribute that may be exploited when one considers designing strategies aimed at disrupting MDR in this pathogenic fungi. Here, we discuss recent advances that have been made in our understanding of fungal micronutrient acquisition and explore the probable pathways that may be utilized as targets.
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6.
Role of Transition Metals in Layered Double Hydroxides for Differentiating the Oxygen Evolution and Nonenzymatic Glucose Sensing.
Moolayadukkam, S, Thomas, S, Sahoo, RC, Lee, CH, Lee, SU, Matte, HSSR
ACS applied materials & interfaces. 2020;(5):6193-6204
Abstract
Layered double hydroxides (LDH) belong to the class of two-dimensional materials having a wide variety of applications ranging from energy storage to catalysis. Often, these materials when used for nonenzymatic electrochemical glucose sensing tend to be interfering with oxygen evolution reaction (OER), resulting in overestimation of the glucose. Herein, to address this, NiFe-based LDH were selected because of their ability to vary the metal ratios. The synthesized LDH have been characterized using various spectroscopic and microscopic techniques. Among the LDH synthesized, Ni4Fe-LDH have been able to differentiate the glucose oxidation potential and the onset potential of OER with minimum interference. The Ni4Fe-LDH sensor shows a sensitivity of 20.43 μA mM-1 cm-2 in the linear range of 0-4 mM concentrations. To further enhance the sensitivity, composites of reduced graphene oxide (rGO) have been synthesized in situ, and the Ni4Fe/rGO5 composites have shown an increased sensitivity of 176.8 μA mM-1 cm-2 attributed to the charge-transfer interactions. To understand the experimental observations, detailed computational studies have been carried out to study the effect of the electronic structure on the metal ratios of the LDH and its role in differentiating glucose sensing and the oxygen evolution reaction. Along with this, theoretical calculations are also carried out on LDH-graphene composites to study the charge-transfer interactions.
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7.
Metabolic manipulation by Pseudomonas fluorescens: a powerful stratagem against oxidative and metal stress.
MacLean, A, Bley, AM, Appanna, VP, Appanna, VD
Journal of medical microbiology. 2020;(3):339-346
Abstract
Metabolism is the foundation of all living organisms and is at the core of numerous if not all biological processes. The ability of an organism to modulate its metabolism is a central characteristic needed to proliferate, to be dormant and to survive any assault. Pseudomonas fluorescens is bestowed with a uniquely versatile metabolic framework that enables the microbe to adapt to a wide range of conditions including disparate nutrients and toxins. In this mini-review we elaborate on the various metabolic reconfigurations evoked by this microbial system to combat reactive oxygen/nitrogen species and metal stress. The fine-tuning of the NADH/NADPH homeostasis coupled with the production of α-keto-acids and ATP allows for the maintenance of a reductive intracellular milieu. The metabolic networks propelling the synthesis of metabolites like oxalate and aspartate are critical to keep toxic metals at bay. The biochemical processes resulting from these defensive mechanisms provide molecular clues to thwart infectious microbes and reveal elegant pathways to generate value-added products.
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8.
Biocrusts buffer against the accumulation of soil metallic nutrients induced by warming and rainfall reduction.
Moreno-Jiménez, E, Ochoa-Hueso, R, Plaza, C, Aceña-Heras, S, Flagmeier, M, Elouali, FZ, Ochoa, V, Gozalo, B, Lázaro, R, Maestre, FT
Communications biology. 2020;(1):325
Abstract
The availability of metallic nutrients in dryland soils, many of which are essential for the metabolism of soil organisms and vascular plants, may be altered due to climate change-driven increases in aridity. Biocrusts, soil surface communities dominated by lichens, bryophytes and cyanobacteria, are ecosystem engineers known to exert critical functions in dryland ecosystems. However, their role in regulating metallic nutrient availability under climate change is uncertain. Here, we evaluated whether well-developed biocrusts modulate metallic nutrient availability in response to 7 years of experimental warming and rainfall reduction in a Mediterranean dryland located in southeastern Spain. We found increases in the availability of K, Mg, Zn and Na under warming and rainfall exclusion. However, the presence of a well-developed biocrust cover buffered these effects, most likely because its constituents can uptake significant quantities of available metallic nutrients. Our findings suggest that biocrusts, a biotic community prevalent in drylands, exert an important role in preserving and protecting metallic nutrients in dryland soils from leaching and erosion. Therefore, we highlight the need to protect them to mitigate undesired effects of soil degradation driven by climate change in this globally expanding biome.
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9.
Compatibility of Phase Change Materials and Metals: Experimental Evaluation Based on the Corrosion Rate.
Ostrý, M, Bantová, S, Struhala, K
Molecules (Basel, Switzerland). 2020;(12)
Abstract
The construction and maintenance of building stock is responsible for approximately 36% of all CO2 emissions in the European Union. One of the possibilities of how to achieve high energy-efficient and decarbonized building stock is the integration of renewable energy sources (RES) in building energy systems that contain efficient energy storage capacity. Phase Change Materials (PCMs) are latent heat storage media with a high potential of integration in building structures and technical systems. Their solid-liquid transition is specifically utilized for thermal energy storage in building applications. The typically quite old example is the use of ice that serves as long-term storage of cold. Large pieces of ice cut in winter were stored in heavily insulated spaces and prepared for cooling of food or beverages in summer. In the contemporary use of the principle, the PCMs for building applications and tested in this study must have a melting range close to the desired temperature in the occupied rooms. As the PCMs need to be encapsulated, several types of metal containers have been developed and tested for their thermal conductivity and resistance to mechanical damage, which enhances the performance of these so-called latent heat thermal energy storage (LHTES) systems. Long-term compatibility of metals with PCMs depends, i.e., on the elimination of an undesirable interaction between the metal and the specific PCM. Heat storage medium must be reliably sealed in a metal container, especially if the LHTES is integrated into systems where PCM leaks can negatively affect human health (e.g., domestic hot water tanks). The aim of this study is to evaluate the interactions between the selected commercially available organic (Linpar 17 and 1820) and inorganic (Rubitherm SP22 and SP25) PCMs and metals widely used for PCM encapsulation (aluminum, brass, carbon steel, and copper). The evaluation is based on the calculation of the corrosion rate (CR), and the gravimetric method is used for the determination of the weight variations of the metal samples. The results show good compatibility for all metals with organic PCMs, which is demonstrated by a mass loss as low as 2.1 mg in case of carbon steel immersed in Linpar 1820 for 12 weeks. The exposure of metals to organic PCMs also did not cause any visual changes on the surface except for darker stains, and tarnishing occurred on the copper samples. More pronounced changes were observed in metal samples immersed in inorganic PCMs. The highest CR values were calculated for carbon steel exposed to inorganic PCM Rubitherm SP25 (up to 13.897 mg·cm-2·year-1). The conclusion of the study is that aluminum is the most suitable container material for the tested PCMs as it shows the lowest mass loss and minimal visual changes on the surface after prolonged exposure to the selected PCMs.
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10.
Direct and indirect influence of arbuscular mycorrhizae on enhancing metal tolerance of plants.
Janeeshma, E, Puthur, JT
Archives of microbiology. 2020;(1):1-16
Abstract
The acerbic elevation of toxic metal ions in arable lands, enhance the risk of their accumulation and biomagnification in crops as well as in humans. Phytoremediation is an eco-friendly approach to clear metal-contaminated lands by making use of metal accumulation potential of plants; which are referred to as hyperaccumulators. This phytoremediation potential can be enhanced with the symbiotic association between the root of hyperaccumulators and arbuscular mycorrhizae. Modification of root morphology, enhancement of antioxidants biosynthesis, and the increase in shoot biomass are the changes observed in plants as a result of indirect influence of arbuscular mycorrhizae. Direct influence of arbuscular mycorrhizae on enhancing metal tolerance of plants includes immobilization strategies, adsorption of metals on to the hyphal wall and glomalin exudation. Furthermore, we have discussed arbuscular mycorrhizal induced increment in the metal tolerance potential of plants through the alteration in various metabolic processes with special emphasis to the phenylpropanoid pathway.