Toxic Effects Of Metals Research Articles

Response of Plant Endophyte Communities to Heavy Metal Stress and Plant Growth Promotion by the Endophyte Serratia marcescens (Strain JG1)

Effects of heavy metals on soil microbial communities have been extensively studied due to their persistence in the environment and imposed threats to living organisms; however, there is a lack of in-depth studies of the impacts of heavy metals on plant endophyte communities. Therefore, the responses of plant endophyte communities to different concentrations of heavy metals were investigated in this study. The endophyte communities of plants existing in severely (W1, Pb, 110.49 mg/kg, Cd, 1.11 mg/kg), moderately (W2, Pb, 55.06 mg/kg, Cd, 0.48 mg/kg), and mildly (W3, Pb, 39.06 mg/kg, Cd, 0.20 mg/kg) contaminated soils were analyzed by 16s rRNA high-throughput Illumina sequencing. Furthermore, networks were constructed to illustrate the relationships between microorganisms and environmental factors. High-quality sequences were clustered at a 97% similarity level. Results revealed that the diversity of the community and relative abundance of Cyanobacteria phylum increased with decreasing levels of pollution. Cyanobacteria and Proteobacteria were found to be the dominant phylum, while Methylobacterium and Sphingomonas were observed as the dominant genus. Tukey’s HSD test showed that the relative abundances of Cyanobacteria and Proteobacteria phyla and Methylobacterium and Sphingomonas genera differed significantly (p < 0.01) among the plants of the three sample sites. Environmental factor analysis revealed a significant negative correlation (p < 0.01) of Cyanobacteria and a significant positive correlation (p < 0.01) of Methylobacterium with the heavy metal content in the environment. These findings suggest that Cyanobacteria and Methylobacterium may be phylum and genus indicators, respectively, of heavy metal toxicity. Tax4Fun analysis showed the effect of heavy metal toxicity on the abundance of genes involved in plant metabolism. In addition, culturable endophytic strains were isolated to study their resistance to heavy metal stress and their ability to promote plant growth. The potting tests showed that the JG1 strain was tolerant to heavy metals, and it could significantly promote the growth of the host plant under stress caused by multiple heavy metals. Compared to the control, the JG1-treated plants showed a 23.14% increase in height and a 12.84% increase in biomass. Moreover, AP, AK, and HN contents in JG1-treated plants were 20.87%, 12.55%, and 9.03% higher, respectively, under heavy metal stress. The results of this study provide a scientific basis for the construction of an efficient plant endophyte restoration system.

Responses to exogenous elicitor treatment in lead-stressed Oryza sativa L.

Heavy metal toxicity adversely affects plants by changing physiological, biochemical, and molecular mechanisms. Lead (Pb) is one of the most common heavy metal pollutants. Hence this study investigated changes caused by exogenous methyl jasmonate (MeJA; 20 and 100 µM) and salicylic acid (SA; 2 and 20 mM) elicitors in local Karacadağ rice exposed to Pb stress (0, 100, and 400 ppm). The effects of elicitors on photosynthetic pigment content (chlorophyll a, chlorophyll b, and total carotenoid), proline, malondialdehyde (MDA), total phenolic and flavonoid, Pb, and total protein contents in stressed plants were evaluated. All parameters studied increased and decreased at varying rates in the treatment groups compared to the Pb-free group (control), indicating that rice plants were affected by Pb stress. The elicitors (MeJA, SA, and MeJA + SA) were applied by foliar spraying. The elicitor treatments increased photosynthetic pigment content, total protein, proline, total flavonoid, and phenolic contents depending on the elicitor type and concentration. MDA and Pb contents, increasing with Pb toxicity, decreased with elicitor treatments, and the stress degree was reduced. When the elicitors were compared, SA was more effective than MeJA in total flavonoid content at 400 ppm Pb toxicity. However, MeJA was more effective in photosynthetic pigment contents, MDA, total protein, Pb, total phenolic, and proline contents. The best results for all parameters examined in rice plants exposed to Pb toxicity were obtained from the 400 ppm Pb + 2 mM SA + 20 µM MeJA treatment group. In conclusion, this study showed that the combined application of MeJA + SA alleviated the harmful effects of Pb by reducing MDA and increasing photosynthetic pigments, total protein, proline, and secondary metabolites, especially at high Pb concentrations. Consequently, this study demonstrated that the combined use of MeJA and SA in rice plants eliminated the negative effects of stress quite effectively, even at high Pb concentrations. Therefore, future studies should focus on the synergistic application of different elicitors to better understand the effects of heavy metal toxicity on plant growth and development.

Spatial distribution, ecological and ecotoxicity evaluation of heavy metals in agricultural soils along Lala-Manjo Highway, Cameroon Volcanic Line

This study aims at assessing the spatial distribution, ecological and toxicity levels of heavy metals in agricultural soils of Lala-Manjo Highway in Cameroon. The soil samples were collected and analyzed by inductively coupled plasma-mass spectrometry. The result shows that Co, Cr, Cu, Hg, Mn, Ni, Sr, V and Zn concentrations are higher than those of the upper continental crust reference values except those of As, Cd and Pb. Correlation coefficient indicate similar input sources governed by same geochemical characteristics. Spatial distribution maps show high concentration of heavy metals in east, south and western part of the study area. Pollution indicators show that enrichment factor varied from moderate to high enrichment of heavy metals. The contamination degree (27.12–35.59), geo-accumulation index (0.01–4.94), and potential ecological risk index (RI = < 150) revealed a low to moderate levels of metallic pollution. The majority of stations have pollution load index and Nemerow integrated pollution index values greater than one, indicating serious pollution. Modified hazard quotient and toxic risk index suggest significant severity of pollution and low toxicity risk of heavy metals, pointing low toxicity effects of heavy metals to fauna and flora in the soil ecosystem. Considering the factors governing soils accumulation such as geology, climate and anthropogenic activities as well as the correlation with commonly used environmental background, it is proposed that the data from this study can be considered as a baseline of pollution to plan major agricultural developments in the area. The study underlines the importance of continuous monitoring and adaptive management for the preservation of soil ecosystem. The results may assist companies and local population in setting realistic targets for monitoring and remediation programs.

Synergistic role of phenylpropanoid biosynthesis and citrate cycle pathways in heavy metal detoxification through secretion of organic acids

Excessive heavy metal contaminants in soils have serious ecological and environmental impacts, and affect plant growth and crop yields. Phytoremediation is an environmentally friendly means of lowering heavy metal concentrations in soils. In this study, we analyzed phenotypic and physiological traits, and the transcriptome and metabolome, of sheepgrass (Leymus chinensis) exposed to cadmium (Cd), lead (Pb), or zinc (Zn). Phenotypic and physiological analysis indicated that sheepgrass had strong tolerance to Cd/Pb/Zn. Transcriptomic analysis revealed that phenylpropanoid biosynthesis and organic acid metabolism were enriched among differentially expressed genes, and metabolomic analysis indicated that the citrate cycle was enriched in response to Cd/Pb/Zn exposure. Genes encoding enzymes involved in the phenylpropanoid and citrate cycle pathways were up-regulated under the Cd/Pb/Zn treatments. Organic acids significantly reduced heavy metal accumulation and improved sheepgrass tolerance of heavy metals. The results suggest that synergistic interaction of the phenylpropanoid and citrate cycle pathways in sheepgrass roots induced organic acid secretion to alleviate heavy metal toxicity. A cascade of enzymes involved in the interacting pathways could be targeted in molecular design breeding to enhance phytoremediation.

Impact of Heavy Metal Contamination on Soil and Crop Ecosystem with Advanced Techniques to Mitigate Them

Heavy metal pollution in soils has become widespread globally due to both natural processes and human activities. Geologic and anthropogenic activities, such as mining, industrial processes, and agricultural practices, significantly contribute to heavy metal accumulation in soil, posing threats to both plant and animal health. These metals endure in the environment and build up in organisms because they resist breakdown or metabolism. They enter the food chain via primary producers and move up as higher trophic levels consume them. This contamination adversely affects the overall human health, plant growth, performance, and yield and also impacts the soil properties. To minimize this effect of heavy metal toxicity, bioremediation emerges as a highly effective method for treating such polluted soils, often conducted in situ, making it suitable for crop establishment or reestablishment. Bioremediation encompasses various techniques like bioventing, biostimulation, air sparging, natural attenuation, phytoremediation, vermistabilization, rhizofiltration, biosorption etc. Both microorganisms and plants play crucial roles in bioremediation, with the combined approach ensuring more efficient cleanup. However, the success of this method depends significantly on the specific species involved. Traditional physical and chemical remediation methods are often costly and fail to restore soil suitability for plant growth. In contrast, bioremediation offers a more environmentally friendly and economically viable solution, leveraging natural processes to encourage plant growth on contaminated soils.

Effect of Enzymes, Biotic, Abiotic Stresses and Metal Toxicity in Brassica napus

Canola is an important crop with low levels of fatty acid and genetically produced from rapeseed. Canola oil is obtained by extract sources. Heavy metals are a unique form of toxin because they may exist in the environment for a longer period. Exogenous administration of gibberellic acid has been proven in several studies to increase crop output by affecting an important physiological process. This study of the aimed and objectives included the nickel sulphate stress in quantity 300 µM and gibberellic acid in quantity 0.25 mM in specific quantity and their effects on different plant functions. Super canola under stress condition when 0.25 mM GA3 was applied. Whereas, minimum reduction was observed in cv. Sherilla under stress condition when 0 mM GA3 was applied. Maximum Catalase was observed in cv. Results showed the Peroxidase (POD), catalase (CAT) and superoxide dismutase (SOD) are the most important protective enzyme systems in plants, and also the most important reactive oxygen species clearance system. Maximum Total Amino acid was observed in cv. Sherilla under control condition when 0 mM GA3 was applied. However, effect of GA3 application was observed non-significant and same for as varietal difference among two genotypes was observed non-significant. Overall, super canola performed better under stress or non-stress condition. Mustard plants exposed to nickel showed decreased morphological characteristics, which might be related to the degradation of plant architecture, which limits the capacity of water content and minerals absorption by plants, resulting in total development of plant loss.

Effect of chromium and cations concentration on stress enzymes in spinach crop grown under vertisol of central India

Interaction of chromium (Cr) metal ions with sodium (Na) and calcium (Ca) and their effect on the different plant enzymes in spinach were evaluated in a glass house experiment. Multi-metal toxicity hampers the crop's growth and affects the uptake kinetics of minerals and other substances from root to edible part. In this experiment, three levels of Cr (0, 50 and 100 mg/kg), Na levels (0, 40, 80 mM), and Ca levels (0, 2, 4 mM) were applied to Indian vertisol. The spinach crop was grown with recommended agronomic practices. Fully tender leaves were taken to measure stress enzymes (catalase, superoxide dismutase (SOD), peroxidase) of metals; and found to have a significant effect on metal toxicity in spinach crop. Increasing the Cr level up to 100 mg/kg significantly enhanced the activities of catalase, SOD, and peroxidase in spinach; whereas, a lower level of Ca and Na with 50 mg Cr/kg soil significantly (p < 0.05) didn't affect the stress enzymes level. However, increasing the salt ions concentration up to 4 mM of Ca and 80 mM of Na with 50 and 100 mg Cr/kg soil enhanced the catalase, peroxidase and SOD activities from 1.61 to 5.42 mg protein/min, 4.26–59.87 mg protein/min and 4.36–64.42 g/fresh weight, respectively. The SOD activity was measured to be more than the catalase and peroxidase under the interactive effect of salt ions and Cr. Such an experiment is useful to identify a metal's toxic effect on crops grown under poor-quality natural resources for executing efficient management strategies for better crop yield.

A Review on Effects of Heavy Metal Toxicity on Plant Growth

A Review on Effects of Heavy Metal Toxicity on Plant Growth

The Effectiveness of Levamisole and Broccoli in Lead Poisoning: Hematobiochemical Changes and Tissue Damage in the Liver, Kidney, and Spleen of Wistar Rats.

Lead, a heavy metal, has emerged as one of the most significant pollutants, bearing irreversible consequences on human and animal health in conjunction with industrial development. Presently, the use of medicinal plants to alleviate the adverse effects of heavy metal toxicity has captured the attention of researchers. Hence, the objective of this study was to assess the impact of levamisole and broccoli extract on the electrophoretic pattern of serum proteins, hematological parameters, and histopathological alterations in the liver, kidney, and spleen tissues within a lead poisoning model of rats. This experimental investigation spanned 28 days, involving 42 male Wistar rats categorized into seven groups: a control group, a lead acetate (AL) group administered at 1000 ppm in drinking water, a broccoli (B) group at 300 mg/kg/day, a levamisole (LE) group at 2.5 mg/kg/day, and combination groups of lead and broccoli (AL + B), lead and levamisole (AL + LE), and lead, broccoli, and levamisole (AL + LE + B). Upon completion of the study, hematological and biochemical parameters were assessed, and serum protein concentrations were analyzed using electrophoresis. Liver, kidney, and spleen tissues were fixed and subjected to histopathological examination with H&E staining. The findings indicated a significant decrease in white blood cells (WBC), red blood cells (RBC), and hemoglobin (Hb) levels in the AL group compared to other groups (p < 0.01). Conversely, the B group exhibited a notable increase in RBC and WBC compared to the AL group (p < 0.05). The most pronounced lead-induced damage was observed in the liver, resulting in elevated levels of specific enzymes such as AST and ALT in the AL group, accompanied by a decline in albumin and total protein (p < 0.001). A reduction in globulin levels, including Beta-2 globulin, was noted in the AL + B and AL + LE groups compared to the AL group (p < 0.001, p < 0.05). Histopathological findings also unveiled increased infiltration of inflammatory cells and hemorrhage in the liver tissue, followed by the spleen, significantly higher in the AL group compared to other experimental groups (p < 0.05). Additionally, congestion and inflammation were evident in the spleen tissue compared to other groups. These tissue damages were mitigated in other combination treatment groups. Based on the aforementioned results, the combination of broccoli and levamisole is deemed effective in ameliorating liver and spleen injuries caused by lead and enhancing biochemical parameters and serum proteins.

Trehalose Induced regulations in Physio-biochemical attributes of Helianthus annuus under Lead stress

Heavy metal is a substantially severe abiotic environmental stress that is rising in many regions of the world. Current climate change circumstances and rapid industrialization increased heavy metal accumulation in soil and water. Overall, worldwide agricultural production decreased. Trehalose, a well-known plant growth regulator, is crucial in plants' responses to a variety of abiotic conditions. The Morpho-physiological and biochemical parameters were analyzed in hydroponic research to identify the possible role of trehalose in alleviating heavy metal lead acetate stress in sunflower (Helianthus annuus L.) crops. In the sole and mixed form, two Pb(C2H3O2)2 (Control and 30 micron) and one trehalose (50 M L-1) levels were used, and a half-strength Hoagland solution was used as a nutritional medium. The current study found that heavy metal stress had a significant negative impact on plant growth (root and shoot length), fresh and dry biomass, and plant water relations, as well as poor plant water relations, membrane stability, chlorophyll content, and antioxidant enzyme activities such as superoxide dismutase (SOD), peroxide (POD), ascorbate peroxide (APX), and catalase (CAT). MDA and H2O2 are the stress markers reduced by the application of trehalose. Exogenous treatment of trehalose, on the other hand, significantly mitigates the detrimental effects of metal toxicity by altering plant physiology, enhancing water relations, and providing robust antioxidant defense against heavy metal lead acetate stress. The findings of this study provide a new dimension to scientists' understanding of the beneficial usage of trehalose in plant science and offer up new research opportunities.

Potential Protective Effects of Spirulina (Spirulina platensis) against In Vitro Toxicity Induced by Heavy Metals (Cadmium, Mercury, and Lead) on SH-SY5Y Neuroblastoma Cells

Spirulina, a filamentous microalga, is used all over the world as a nutraceutical dietary supplement. Recent studies have focused on examining its chelating activity and antioxidant properties, especially as a candidate for protection against neurotoxicity caused by heavy metals. The MTT test and LDH assay were used to examine the viability of the SH-SY5Y cells for 24, 48, and 72 h, to Cd, Hg, and Pb, individually or in combination with Spirulina, and the effects of necrotic cell death. In comparison to the control group, the viability of SH-SY5Y cells decreased after 24 h of exposure, with Cd being more toxic than Hg and Pb being less lethal. The effects of heavy metal toxicity on cell survival were ranked in order after 72 h under identical experimental circumstances as follows: Hg, Pb, and Cd. The viability of the cells was then tested after being exposed to Spirulina at doses of 5 at 50 (%v/v) for 24, 48, and 72 h, respectively. SH-SY5Y cells that had been treated with mixtures of heavy metals and Spirulina underwent the same assay. Cell viability is considerably increased by using Spirulina treatments at the prescribed periods and doses. Instead, the same procedure, when applied to SH-SY5Y cells, caused the release of LDH, which is consistent with the reduction in cell viability. We demonstrated for the first time, considering all the available data, that Spirulina 5, 25, and 50 (%v/v) enhanced the number of viable SH-SY5Y cells utilized as a model system for brain cells. Overall, the data from the present study provide a first insight into the promising positive role of Spirulina against the potentially toxic effects of metals.

Hazardous effects of heavy metal toxicity on soil and plants and their bioremediation: a review

Heavy metal-polluted soils have grown ubiquitous worldwide due to increased geologic and anthropogenic activity, and the plants growing in these soils exhibit decreased growth, performance, and yield. Contaminated soil with heavy metals has become a concern for agricultural scientists because of the progress made in agricultural product safety. Heavy metals are metalloids with biological toxicity. The most common are arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), lead (Pb), and zinc (Zn). These metals exist throughout the terrestrial environment and have spread out due to anthropogenic and natural activities. Soil heavy metal pollution leads to human health risks, groundwater pollution, plant phytotoxicity, and a decline in crop and soil production. Bioremediation is an effective method of treating heavy metal-polluted soils. It is a widely accepted method that is mostly carried out in situ; hence it is suitable for the establishment/reestablishment of crops on treated soils. Using plants in the treatment of polluted soils is a more common approach in the bioremediation of heavy metal-polluted soils. Bioremediation ensures a more efficient clean-up of heavy metal-polluted soils. However, the success of this approach largely depends on the species of organisms. This paper is aimed to review the hazardous effects of heavy metal toxicity on soil and plants and their bioremediation. This paper also discusses numerous strategies for addressing heavy metal contamination in soil. Keywords: heavy metals, anthropogenic sources, natural sources, bioremediation

A Critical Review on Sulphur Application in Rapeseed-mustard to Enhancing Productivity and Oil Quality

Sulfur (S) plays a vital role in determining the seed yield, oil content, quality, and resistance to various stresses in rapeseed-mustard. It is essential for chlorophyll formation, oil synthesis, seed protein, amino acids, enzymes, and glucosinolate in these plants. Sulphur also boosts mustard seed production. However, due to modern agricultural practices, including multiple cropping, the use of sulfur-free fertilizers, and limited organic manure application, soil sulfur levels are depleting rapidly in India. Indian soils typically contain between 10 to 6319 mg kg-1 of sulfur, with most agricultural soils averaging 30 to 300 mg kg-1. Adding sulfur increases mustard oil content by enhancing the activity of an enzyme called acetyl-CoA carboxylase, which is essential for oil synthesis. Sulfur also mitigates the harmful effects of heavy metal toxicity, especially from cadmium. Sulfur interacts with other nutrients in both positive and negative ways. Recommendations for sulfur fertilization in different mustard growing regions have been made based on various research programs. To maximize sulfur use efficiency, it's crucial to apply the correct amount based on soil tests and in balance with other limiting nutrients. Timing of sulfur application is also important; it's best applied at the beginning but can also be top-dressed 20-40 days after planting for optimal yield. Research suggests that mustard responds well to foliar spraying of thiourea during flowering and basal placement before sowing. This paper reviews the strategies to improve sulfur utilization through advancements in application rates, methods, and sulfur sources on rapeseed-mustard.

Effects of Heavy Metal Toxicity on Different Animal Models

Abstract: Due to the widespread environmental contamination caused by heavy metal toxicity, is becoming a growing threat to all biological life form on Earth. In this case animal models play had an urgent impact in figuring out the impacts of heavy metal exposure on different animal species. The negative effects of heavy metals such as Hg, Pb, Cr, Cd, and as has been seen in animals’ models to cause damage to various organs such as nervous, respiratory and reproductive systems. Additionally, the translational implications for human health and differences in animal sensitivity to heavy metal toxicity are also investigated. This survey study aims to provide a thorough overview of how heavy metal poisoning affects diverse animal models. The advantages and disadvantages of various animal models for heavy metal toxicity research are highlighted in this discussion. This review emphasizes the need for additional research in this area and the significance of animal studies in elucidating the dangers and potential effects of heavy metal toxicity.

Mitigating the negative effects of lead toxicity on Vigna mungo: The promising role of rhizobacteria

Growing Vigna mungo in soils contaminated with lead (Pb) is a major concern due to its negative impact on plant growth and development. When lead enters through food in the human body, it can be accumulated in bones, liver, and kidneys. In severe cases, lead poisoning can cause cancer, seizures, coma, and even death. To address this issue in plants, phosphate-solubilizing bacteria (PSB) have been identified as a potential solution to enhance plant growth and mitigate the harmful effects of heavy metal toxicity. However, the effectiveness of PSB can be improved by isolating and characterizing new strains over time, which will aid in developing sustainable management strategies for Pb-contaminated soils. Thus, the current study aimed to investigate the impact of Pb contamination on V. mungo growth and the potential use of newly isolated microbial strains to enhance V. mungo growth and immobilize Pb. Three levels of Pb contamination were used: control (no Pb toxicity), 125Pb (125 mg Pb/kg soil), and 250Pb (250 mg Pb/kg soil). Six different microbial strains, RP01, RP02, RP03, RP04, RP05, and RP06, were used to inoculate V. mungo seeds. The results of the experiment demonstrated that RP02 was the most effective strain in improving various growth parameters such as shoot length, root length, seedling length, fresh weight, dry weight, chlorophyll a, chlorophyll b, and total chlorophyll. While RP03 also showed significant improvement in these growth parameters, its effectiveness was not as high as RP02 in some respects. The efficacy of RP02 in alleviating Pb toxicity was further confirmed by a significant decrease in Pb concentration in the seedling, which was attributed to the production of siderophore. Therefore, it can be concluded that RP02 has the potential to improve V. mungo growth under Pb contamination. However, further field investigations are needed to confirm RP02 as the best strain for enhancing V. mungo production under Pb toxicity.

The role of hypoxia-inducible factor 1 alpha (HIF-1α) modulation in heavy metal toxicity.

Hypoxia-inducible factor 1 (HIF-1) is an oxygen-sensing transcriptional regulator orchestrating a complex of adaptive cellular responses to hypoxia. Several studies have demonstrated that toxic metal exposure may also modulate HIF-1α signal transduction pathway, although the existing data are scarce. Therefore, the present review aims to summarize the existing data on the effects of toxic metals on HIF-1 signaling and the potential underlying mechanisms with a special focus on prooxidant effect of the metals. The particular effect of metals was shown to be dependent on cell type, varying from down- to up-regulation of HIF-1 pathway. Inhibition of HIF-1 signaling may contribute to impaired hypoxic tolerance and adaptation, thus promoting hypoxic damage in the cells. In contrast, its metal-induced activation may result in increased tolerance to hypoxia through increased angiogenesis, thus promoting tumor growth and contributing to carcinogenic effect of heavy metals. Up-regulation of HIF-1 signaling is mainly observed upon Cr, As, and Ni exposure, whereas Cd and Hg may both stimulate and inhibit HIF-1 pathway. The mechanisms underlying the influence of toxic metal exposure on HIF-1 signaling involve modulation of prolyl hydroxylases (PHD2) activity, as well as interference with other tightly related pathways including Nrf2, PI3K/Akt, NF-κB, and MAPK signaling. These effects are at least partially mediated by metal-induced ROS generation. Hypothetically, maintenance of adequate HIF-1 signaling upon toxic metal exposure through direct (PHD2 modulation) or indirect (antioxidant) mechanisms may provide an additional strategy for prevention of adverse effects of metal toxicity.

Nanoplastics potentiate mercury toxicity in a marine copepod under multigenerational exposure

The continuous fragmentation of plastics and release of synthetic nanoplastics from products have been aggravating nanoplastic pollution in the marine ecosystem. The carrier role of nanoplastics may increase the bioavailability and toxicity effects of toxic metals, e.g., mercury (Hg), which is of growing concern. Here, the copepod Tigriopus japonicus was exposed to polystyrene nanoplastics (PS NPs) and Hg (alone or combined) at environmental realistic concentrations for three generations (F0-F2). Then, Hg accumulation, physiological endpoints, and transcriptome were analyzed. The results showed that the copepod's reproduction was significantly inhibited under PS NPs or Hg exposure. The presence of PS NPs caused significantly higher Hg accumulation, lower survival, and lower offspring production in copepods relative to Hg exposure, suggesting an increased threat to the copepod's survivorship and health. From the molecular perspective, combined PS NPs and Hg caused a graver effect on the DNA replication, cell cycle, and reproduction pathways relative to Hg exposure, linking to lower levels of survivorship and reproduction. Taken together, this study provides an early warning of nanoplastic pollution for the marine ecosystem not only because of their adverse effect per se but also their carrier role for increasing Hg bioaccumulation and toxicity in copepods.

Metal tolerance mechanisms in plants and microbe-mediated bioremediation

The heavy metal contamination, which causes toxic effects on plants, has evolved into a significant constraint to plant quality and yield. This scenario has been exacerbated by booming population expansion and intrinsic food insecurity. Numerous studies have found that counteracting heavy metal tolerance and accumulation necessitates complex mechanisms at the biochemical, molecular, tissue, cellular and whole plant levels, which may demonstrate increased crop yields. Essential and non-essential elements have similar harmful impacts on plants including reduced biomass production, growth and photosynthesis inhibition, chlorosis, altered fluid balance and nutrient absorption, as well as senescence, all of which led to plant death. Notable biotechnological strategies for effective remediation require knowledge of metal stress and tolerance mechanisms in plants. Assimilation, cooperation and integration, of biotechnological improvements, are required for adequate environmental rehabilitation in the emerging area of bioremediation. This review emphasizes a deeper understanding of metal toxicity, stress, and potential tolerance mechanisms in plants exposed to metal stress. The microbe-mediated metal toxic effects and stress mitigation knowledge can be used to create a new strategic plan as feasible, sustainable, and environmentally friendly bioremediation techniques.

Metal-protein solution interactions investigated using model systems: Thermodynamic and spectroscopic methods.

The first-row D-block metal ions are essential for the physiology of living organisms, functioning as cofactors in metalloproteins or structural components for enzymes: almost half of all proteins require metals to perform the biological function. Understanding metal-protein interactions is crucial to unravel the mysteries behind molecular biology, understanding the effects of metal imbalance and toxicity or the diseases due to disorders in metal homeostasis. Metal-protein interactions are dynamic: they are noncovalent and affected by the environment to which the system is exposed. To reach a complete comprehension of the system, different conditions must be considered for the experimental investigation, in order to get information on the species distribution, the ligand coordination modes, complex stoichiometry and geometry. Thinking about the whole environment where a protein acts, investigations are often challenging, and simplifications are required to study in detail the mechanisms of metal interaction. This chapter is intended to help researchers addressing the problem of the complexity of metal-protein interactions, with particular emphasis on the use of peptides as model systems for the metal coordination site. The thermodynamic and spectroscopic methods most widely employed to investigate the interaction between metal ions and peptides in solution are here covered. These include solid-phase peptide synthesis, potentiometric titrations, calorimetry, electrospray ionization mass spectrometry, UV-Vis spectrophotometry, circular dichroism (CD), nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR). Additional experimental methods, which can be employed to study metal complexes with peptides, are also briefly mentioned. A case-study is finally reported providing a practical example of the investigation of metal-protein interaction by means of thermodynamic and spectroscopic methods applied to peptide model systems.

Evaluation of toxicity and resistant effects of heavy metals and antibiotics on the growth of marine bioluminescent bacteria

Luminescence is the emission of light by an object. Living organisms including certain bacteria are capable of luminescence. Bacteria are the most abundant luminescent organisms in nature. Bacterial luminescence has been studied most extensively in several marine bacteria. Bacterial luminescence is due to the action of the enzyme called luciferase. The luminescent bacteria exist in nature either as free-living bacteria or in symbiotic association with certain marine organisms. Research on luminescent bacteria has always been a fascinating one. In the present study, ten free living luminescent bacteria initially isolated from marine origin were characterized for their tolerance to heavy metals and antibiotics. Copper, zinc, cobalt and cadmium metals at 1 mg/mL concentration have inhibited the growth and luminescence of the all strains except strains 1, 2 and 7. Surprisingly, lead metal at the same concentration dd not inhibit any of the ten strains. However, at 2 mg/mL concentration, similar trend was observed on the growth and luminescence of all the 10 strains. Also, all the tested isolates were sensitive (1 cm &gt;) to all Gram negative and positive antibiotics being tested except isolates 3, 6 and 8, respectively which were resistant (0 – 0.9 cm) to all the antibiotics tested. Thus, the strains isolated from the different sample types have good beneficial potentials such as heavy metal tolerance and antibiotic sensitivity.