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1.
Siderophore-assisted cadmium hyperaccumulation in Bacillus subtilis.
Khan, A, Gupta, A, Singh, P, Mishra, AK, Ranjan, RK, Srivastava, A
International microbiology : the official journal of the Spanish Society for Microbiology. 2020;(2):277-286
Abstract
Siderophores (Gk iron carriers) are low molecular weight secondary metabolites produced by bacteria, fungi, and plants that have strong binding affinity for iron. Owing to their iron-chelating ability, they are produced mainly when the organism faces iron scarcity. The present study empirically investigated the importance of applying hydroxamate siderophore extracted from Aspergillus nidulans to the cells of Bacillus subtilis for bioremediation of cadmium salt. This investigation deals with siderophore-mediated intracellular Cd accumulation by bacterial cells, growth estimation, biochemical assays like lipid peroxidation, total protein content, carbohydrate content, and iron content estimation. In silico docking and STRING analyses revealed specific interaction between Aspergillus siderophore and receptors present on B. subtilis. Estimation of intracellular Cd by atomic absorption spectroscopy showed more accumulation of Cd ions by B. subtilis in the presence of hydroxamate siderophore. This suggests a possibility of confiscating environmental Cd2+ by utilizing metal chelation property of siderophores and hence can lead to emerging bioremediation mechanisms for heavy metals. In silico studies support experimental investigation and suggest higher affinity of siderophore for Cd ions as compared with ferric ions.
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2.
Removal of toxic metals from wastewater in constructed wetlands as a green technology; catalyst role of substrates and chelators.
Batool, A, Saleh, TA
Ecotoxicology and environmental safety. 2020;:109924
Abstract
In recent years knowledge in regard to phytoremediation for removal of metals from wastewater has been extensively developed. Despite advance treatment methods; different plants were widely used for wastewater treatment that may affect the efficiency of plants by stressing their natural ability. Therefore, this paper reviews the catalytic role of constructed wetlands, spiking of chelators and substrates to enhance phytoremediation for removal of metals. Catalytic combination of substrates, chelators with plants helped to remove different metals from wastewater simultaneously without compromising the plant's health. Moreover, this paper summarizes the interaction mechanism of plants with the chelators and substrates within constructed wetlands. In addition, this paper also discusses the potential research needs for this field.
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3.
Emerging Roles of microRNAs in Plant Heavy Metal Tolerance and Homeostasis.
Ding, Y, Ding, L, Xia, Y, Wang, F, Zhu, C
Journal of agricultural and food chemistry. 2020;(7):1958-1965
Abstract
Heavy metal stress is a major growth- and yield-limiting factor for plants. Heavy metals include essential metals (copper, iron, zinc, and manganese) and non-essential metals (cadmium, mercury, aluminum, arsenic, and lead). Plants use complex mechanisms of gene regulation under heavy metal stress. MicroRNAs are 21-nucleotide non-coding small RNAs as important modulators of gene expression post-transcriptionally. Recently, high-throughput sequencing has led to the identification of an increasing number of heavy-metal-responsive microRNAs in plants. Metal-regulated microRNAs and their target genes are part of a complex regulatory network that controls various biological processes, including heavy metal uptake and transport, protein folding and assembly, metal chelation, scavenging of reactive oxygen species, hormone signaling, and microRNA biogenesis. In this review, we summarize the recent molecular studies that identify heavy-metal-regulated microRNAs and their roles in the regulation of target genes as part of the microRNA-associated regulatory network in response to heavy metal stress in plants.
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4.
Domain exchange between Oryza sativa phytochelatin synthases reveals a region that determines responsiveness to arsenic and heavy metals.
Hayashi, S, Tanikawa, H, Kuramata, M, Abe, T, Ishikawa, S
Biochemical and biophysical research communications. 2020;(2):548-553
Abstract
Phytochelatin synthases (PCSs) are activated by toxic metals/metalloids such as cadmium and arsenic and synthesize phytochelatins for detoxification of toxic elements. Rice (Oryza sativa L.) has two PCSs (OsPCS1 and OsPCS2), and we previously revealed that OsPCS1 has a higher responsiveness to arsenic than to cadmium, while OsPCS2 has a higher responsiveness to cadmium than to arsenic. Moreover, we found that the specific responsiveness of OsPCS1 to arsenic at rice nodes is a key factor in reducing arsenic in rice grains. However, the molecular characteristics of two PCSs in rice that contribute to the responsiveness to arsenic or heavy metals, including Cd, remain unclear. Here, we experimentally demonstrate that the C-terminal region in PCSs determines the responsiveness to arsenic or cadmium. We constructed chimeric proteins between OsPCS1 and OsPCS2 and performed an in vitro phytochelatin synthesis assay. A chimeric protein in which the 183 C-terminal amino acids of OsPCS2 were replaced with the 185 C-terminal amino acids of OsPCS1 showed higher responsiveness to arsenite than to cadmium, similar to OsPCS1. Contrary to expectations, mutations of cysteine residues that are unique to OsPCS1 or OsPCS2 had little influence on the responsiveness, although cysteine residues are reported to be representative of sites that interact with metals/metalloids. These results would enable the development of a breeding technology for reducing arsenic in rice grains by improving the arsenic-dependent activation of PCSs.
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5.
Mechanisms of Co, Ni, and Mn toxicity: From exposure and homeostasis to their interactions with and impact on lipids and biomembranes.
Sule, K, Umbsaar, J, Prenner, EJ
Biochimica et biophysica acta. Biomembranes. 2020;(8):183250
Abstract
Anthropogenic activity has increased human exposure to metals and resulted in metal induced toxicity. Essential trace elements like cobalt (Co), nickel (Ni), and manganese (Mn) are best known for their roles as important cofactors in many enzymes involved in signalling, metabolism, and response to oxidative stress. However, deficiencies as well as long-term overexposure to these metals can result in negative health effects. Co has been associated with cardiomyopathy, lung disease, and hearing damage, while Ni is a known carcinogen, as well as a common sensitizing metal. Mn is best classified as a neurotoxicant that causes a disorder alike to idiopathic Parkinson's disease known as Manganism. Although the mechanisms of Co, Ni, and Mn toxicity are complex and have yet to be fully elucidated, research over the years has provided useful insights into understanding metal-induced detrimental effects at the cellular and molecular level. One area of research that has been explored in less detail are metal interactions with lipids and biological membranes, which are a potentially critical target as membranes are the first point of contact for cells. This review covers the current understandings of Co, Ni and Mn toxicity, in terms of human exposure, homeostasis and mechanisms of transport, potential cellular targets, and, of primary focus, metal interactions with lipid and biomembranes. A variety of effects like membrane rigidification, leakage affecting membrane potentials, lipid phase changes, alterations in lipid metabolism and changes of cellular morphology illustrate the vast potential for metal-based membrane effects contributing to their toxicity.
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6.
Differences in metal tolerance among strains, populations, and species of marine diatoms - Importance of exponential growth for quantification.
Andersson, B, Godhe, A, Filipsson, HL, Rengefors, K, Berglund, O
Aquatic toxicology (Amsterdam, Netherlands). 2020;:105551
Abstract
Strains of microalgae vary in traits between species and populations due to adaptation or stochastic processes. Traits of individual strains may also vary depending on the acclimatization state and external forces, such as abiotic stress. In this study we tested how metal tolerance differs among marine diatoms at three organizational levels: species, populations, and strains. At the species level we compared two pelagic Baltic Sea diatoms (Skeletonema marinoi and Thalassiosira baltica). We found that the between-species differences in tolerance (EC50) to the biologically active metals (Cu, Co, Ni, and Zn) was similar to that within-species. In contrast, the two species differed significantly in tolerance towards the non-essential metals, Ag (three-fold higher in T. baltica), Pb and Cd (two and three-fold higher in S. marinoi). At the population level, we found evidence that increased tolerance against Cu and Co (17 and 41 % higher EC50 on average, respectively) had evolved in a S. marinoi population subjected to historical mining activity. On a strain level we demonstrate how the growth phase of cultures (i.e., cellular densities above exponential growth) modulated dose-response relationships to Ag, Cd, Co, Cu, and Zn. Specifically, the EC50's were reduced by 10-60 % in non-exponentially growing S. marinoi (strain RO5AC), depending on metal. For the essential metals these differences were often larger than the average differences between the two species and populations. Consequently, without careful experimental design, interactions between nutrient limitation and metal stress may interfere with detection of small, but evolutionary and ecologically important, differences in tolerance between microalgae. To avoid such artifacts, we outline a semi-continuous cultivation approach that maintains, and empirically tests, that exponential growth is achieved. We argue that such an approach is essential to enable comparison of population or strain differences in tolerance using dose-response tests on cultures of microalgae.
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7.
Biotechnological Applications of Paenibacillus sp. D9 Lipopeptide Biosurfactant Produced in Low-cost Substrates.
Jimoh, AA, Lin, J
Applied biochemistry and biotechnology. 2020;(3):921-941
Abstract
The present study assesses the Paenibacillus sp. D9 lipopeptide biosurfactant synthesis in cheap substrates including functional properties and applicability for varying biotechnological processes. Different experimental setups were made for oil dispersion, heavy metals removals from contaminated environments, and washing performance. The study revealed surface tension activities of 31.7-32.7 mN/m, and maximum biosurfactant yield of more than 8 g/L. Removals of 85.90%, 98.68%, 99.97%, 63.28%, 99.93%, and 94.22% were obtained for Ca, Cu, Fe, Mg, Ni, and Zn, respectively from acid mine effluents. In comparison with chemical surfactants, there was pronounced removal of heavy metals from wastewater, contaminated sands, and vegetable matter, as well as improved oil dispersing activity. A comparative study revealed that biosurfactant was more efficient (> 60%) for removal of tomato sauce and coffee stains than chemical surfactants (< 50%). Thus, lipopeptide biosurfactants are green biomolecules reducing hazards and contaminations within the environment. The future use of this lipopeptide biosurfactant is greatly promising in biotechnology.
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8.
Nitric oxide-mediated regulation of oxidative stress in plants under metal stress: a review on molecular and biochemical aspects.
Sharma, A, Soares, C, Sousa, B, Martins, M, Kumar, V, Shahzad, B, Sidhu, GPS, Bali, AS, Asgher, M, Bhardwaj, R, et al
Physiologia plantarum. 2020;(2):318-344
Abstract
Given their sessile nature, plants continuously face unfavorable conditions throughout their life cycle, including water scarcity, extreme temperatures and soil pollution. Among all, metal(loid)s are one of the main classes of contaminants worldwide, posing a serious threat to plant growth and development. When in excess, metals which include both essential and non-essential elements, quickly become phytotoxic, inducing the occurrence of oxidative stress. In this way, in order to ensure food production and safety, attempts to enhance plant tolerance to metal(loid)s are urgently needed. Nitric oxide (NO) is recognized as a signaling molecule, highly involved in multiple physiological events, like the response of plants to abiotic stress. Thus, substantial efforts have been made to assess NO potential in alleviating metal-induced oxidative stress in plants. In this review, an updated overview of NO-mediated protection against metal toxicity is provided. After carefully reviewing NO biosynthetic pathways, focus was given to the interaction between NO and the redox homeostasis followed by photosynthetic performance of plants under metal excess.
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9.
Identification and Validation of Reference Genes for RT-qPCR Analysis in Switchgrass under Heavy Metal Stresses.
Zhao, J, Zhou, M, Meng, Y
Genes. 2020;(5)
Abstract
Switchgrass (Panicum Virgatum L.) has been recognized as the new energy plant, which makes it ideal for the development of phytoremediation on heavy metal contamination in soils with great potential. This study aimed to screen the best internal reference genes for the real-time quantitative PCR (RT-qPCR) in leaves and roots of switchgrass for investigating its response to various heavy metals, such as cadmium (Cd), lead (Pb), mercury (Hg), chromium (Cr), and arsenic (As). The stability of fourteen candidate reference genes was evaluated by BestKeeper, GeNorm, NormFinder, and RefFinder software. Our results identified U2AF as the best reference gene in Cd, Hg, Cr, and As treated leaves as well as in Hg, Pb, As, and Cr stressed root tissues. In Pb treated leaf tissues, 18S rRNA was demonstrated to be the best reference gene. CYP5 was determined to be the optimal reference gene in Cd treated root tissues. The least stable reference gene was identified to be CYP2 in all tested samples except for root tissues stressed by Pb. To further validate the initial screening results, we used the different sets of combinatory internal reference genes to analyze the expression of two metal transport associated genes (PvZIP4 and PvPDB8) in young leaves and roots of switchgrass. Our results demonstrated that the relative expression of the target genes consistently changed during the treatment when CYP5/UBQ1, U2AF/ACT12, eEF1a/U2AF, or 18S rRNA/ACT12 were combined as the internal reference genes. However, the time-dependent change pattern of the target genes was significantly altered when CYP2 was used as the internal reference gene. Therefore, the selection of the internal reference genes appropriate for specific experimental conditions is critical to ensure the accuracy and reliability of RT-qPCR. Our findings established a solid foundation to further study the gene regulatory network of switchgrass in response to heavy metal stress.
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10.
Serum trace element and heavy metal levels in patients with sepsis.
Akkaş, İ, Ince, N, Sungur, MA
The aging male : the official journal of the International Society for the Study of the Aging Male. 2020;(3):222-226
Abstract
Background and objectives: Sepsis is defined as a life-threatening organ dysfunction syndrome, which occurs when the body's immune response to infection is impaired. The aim of the present study was to investigate serum Iron, Copper, Zinco, Cobalt, Chromium, Selenium, Vanadium, Nickel, Cadmium, and Aliminium levels in patients with sepsis.Materials and methods: This prospective and observational study was conducted at a tertiary care university hospital of Turkey from 2015 to 2016, and comprised patients with sepsis. Serum concentrations of 10 elements were analyzed using inductively coupled plasma mass spectrometry. Analyses were performed at the laboratory of Düzce University Scientific and Technological Research Application and Research Center. A total of 87 participants (52 men, 35 women; average age, 74.11 ± 14.26) were enrolled.Results: When evaluated in terms of trace elements, a significant difference was noted between the sepsis and control groups in terms of the levels of the five elements. Chromium, Iron, Nickel, Copper, and Cadmium levels were significantly higher in the sepsis group.Conclusion: Our study indicated in particular, Iron, Copper, Chromium, Nickel, and Cadmium levels were elevated in patients with sepsis.