Characterization of metallothionein genes from Broussonetia papyrifera: metal binding and heavy metal tolerance mechanisms.

BACKGROUND: Broussonetia papyrifera is an economically significant tree with high utilization value, yet its cultivation is often constrained by soil contamination with heavy metals (HMs). Effective scientific cultivation management, which enhances the yield and quality of B. papyrifera, necessitates an understanding of its regulatory mechanisms in response to HM stress. RESULTS: Twelve Metallothionein (MT) genes were identified in B. papyrifera. Their open reading frames ranged from 186 to 372 bp, encoding proteins of 61 to 123 amino acids with molecular weights between 15,473.77 and 29,546.96 Da, and theoretical isoelectric points from 5.24 to 5.32. Phylogenetic analysis classified these BpMTs into three subclasses: MT1, MT2, and MT3, with MT2 containing seven members and MT3 only one. The expression of most BpMT genes was inducible by Cd, Mn, Cu, Zn, and abscisic acid (ABA) treatments, particularly BpMT2e, BpMT2d, BpMT2c, and BpMT1c, which showed significant responses and warrant further study. Yeast cells expressing these BpMT genes exhibited enhanced tolerance to Cd, Mn, Cu, and Zn stresses compared to control cells. Yeasts harboring BpMT1c, BpMT2e, and BpMT2d demonstrated higher accumulation of Cd, Cu, Mn, and Zn, suggesting a chelation and binding capacity of BpMTs towards HMs. Site-directed mutagenesis of cysteine (Cys) residues indicated that mutations in the C domain of type 1 BpMT led to increased sensitivity to HMs and reduced HM accumulation in yeast cells; While in type 2 BpMTs, the contribution of N and C domain to HMs' chelation possibly corelated to the quantity of Cys residues. CONCLUSION: The BpMT genes are crucial in responding to diverse HM stresses and are involved in ABA signaling. The Cys-rich domains of BpMTs are pivotal for HM tolerance and chelation. This study offers new insights into the structure-function relationships and metal-binding capabilities of type-1 and - 2 plant MTs, enhancing our understanding of their roles in plant adaptation to HM stresses.

Native desert plants have the potential for phytoremediation of phytotoxic metals in urban cities: implications for cities sustainability in arid environments.

Arid regions can benefit from using native desert plants, which require minimal freshwater and can aid in remediating soil phytotoxic metals (PTMs) from traffic emissions. In this study, we assessed the ability of three native desert plants-Pennisetum divisum, Tetraena qatarensis, and Brassica tournefortii-to accumulate phytotoxic metals (PTMs) in their different plant organs, including leaves, stems, and roots/rhizomes. The PTMs were analyzed in soil and plant samples collected from Dubai, United Arab Emirates (UAE). The results indicated significantly higher levels of PTMs on the soil surface than the subsurface layer. Brassica exhibited the highest concentrations of Fe and Zn, measuring 566.7 and 262.8 mg kg-1, respectively, while Tetraena accumulated the highest concentration of Sr (1676.9 mg kg-1) in their stems. In contrast, Pennisetum recorded the lowest concentration of Sr (21.0 mg kg-1), while Tetraena exhibited the lowest concentrations of Fe and Zn (22.5 and 30.1 mg kg-1) in their leaves. The roots of Pennisetum, Brassica, and Tetraena demonstrated the potential to accumulate Zn from the soil, with concentration factors (CF) of 1.75, 1.09, and 1.09, respectively. Moreover, Brassica exhibited the highest CF for Sr, measuring 2.34. Pennisetum, however, could not translocate PTMs from its rhizomes to other plant organs, as indicated by a translocation factor (TF) of 1. In contrast, Brassica effectively translocated the studied PTMs from its roots to the stem and leaves (except for Sr in the leaves). Furthermore, Pennisetum exclusively absorbed Zn from the soil into its leaves and stems, with an enrichment factor (EF) greater than 1. Brassica showed the ability to uptake the studied PTMs in its stem and leaves (except for Fe), while Tetraena primarily absorbed Sr and Zn into its stems. Based on the CF and TF results, Pennisetum appears to be a suitable species for phytostabilization of both Fe and Zn, while Brassica is well-suited for Sr and Zn polluted soils. Tetraena shows potential for Zn phytoremediation. These findings suggest that these plants are suitable for PTMs phytoextraction. Furthermore, based on the EF results, these plants can efficiently sequester PTMs.

Heavy metals in cigarette smoke strongly inhibit pancreatic ductal function and promote development of chronic pancreatitis.

BACKGROUND AND AIMS: Smoking is recognised as an independent risk factor in the development of chronic pancreatitis (CP). Cystic fibrosis transmembrane conductance regulator (CFTR) function and ductal fluid and bicarbonate secretion are also known to be impaired in CP, so it is crucial to understand the relationships between smoking, pancreatic ductal function and the development of CP. METHODS: We measured sweat chloride (Cl-) concentrations in patients with and without CP, both smokers and non-smokers, to assess CFTR activity. Serum heavy metal levels and tissue cadmium concentrations were determined by mass spectrometry in smoking and non-smoking patients. Guinea pigs were exposed to cigarette smoke, and cigarette smoke extract (CSE) was prepared to characterise its effects on pancreatic HCO3 - and fluid secretion and CFTR function. We administered cerulein to both the smoking and non-smoking groups of mice to induce pancreatitis. RESULTS: Sweat samples from smokers, both with and without CP, exhibited elevated Cl- concentrations compared to those from non-smokers, indicating a decrease in CFTR activity due to smoking. Pancreatic tissues from smokers, regardless of CP status, displayed lower CFTR expression than those from non-smokers. Serum levels of cadmium and mercury, as well as pancreatic tissue cadmium, were increased in smokers. Smoking, CSE, cadmium, mercury and nicotine all hindered fluid and HCO3 - secretion and CFTR activity in pancreatic ductal cells. These effects were mediated by sustained increases in intracellular calcium ([Ca2+]i), depletion of intracellular ATP (ATPi) and mitochondrial membrane depolarisation. CONCLUSION: Smoking impairs pancreatic ductal function and contributes to the development of CP. Heavy metals, notably cadmium, play a significant role in the harmful effects of smoking. KEY POINTS: Smoking and cigarette smoke extract diminish pancreatic ductal fluid and HCO3 - secretion as well as the expression and function of CFTR Cd and Hg concentrations are significantly higher in the serum samples of smokers Cd accumulates in the pancreatic tissue of smokers.

Bioremediation of petroleum refinery wastewater using Bacillus subtilis IH-1 and assessment of its toxicity.

Environmental contamination from petroleum refinery operations has increased due to the rapid population growth and modernization of society, necessitating urgent repair. Microbial remediation of petroleum wastewater by prominent bacterial cultures holds promise in circumventing the issue of petroleum-related pollution. Herein, the bacterial culture was isolated from petroleum-contaminated sludge samples for the valorization of polyaromatic hydrocarbons and biodegradation of petroleum wastewater samples. The bacterial strain was screened and identified as Bacillus subtilis IH-1. After six days of incubation, the bacteria had degraded 25.9% of phenanthrene and 20.3% of naphthalene. The treatment of wastewater samples was assessed using physico-chemical and Fourier-transform infrared spectroscopy analysis, which revealed that the level of pollutants was elevated and above the allowed limits. Following bacterial degradation, the reduction in pollution parameters viz. EC (82.7%), BOD (87.0%), COD (80.0%), total phenols (96.3%), oil and grease (79.7%), TKN (68.8%), TOC (96.3%) and TPH (52.4%) were observed. The reduction in pH and heavy metals were also observed after bacterial treatment. V. mungo was used in the phytotoxicity test, which revealed at 50% wastewater concentration the reduction in biomass (30.3%), root length (87.7%), shoot length (93.9%), and seed germination (30.0%) was observed in comparison to control. When A. cepa root tips immersed in varying concentrations of wastewater samples, the mitotic index significantly decreased, suggesting the induction of cytotoxicity. However, following the bacterial treatment, there was a noticeable decrease in phytotoxicity and cytotoxicity. The bacterial culture produces lignin peroxidase enzyme and has the potential to degrade the toxic pollutants of petroleum wastewater. Therefore the bacterium may be immobilised or directly used at reactor scale or pilot scale study to benefit the industry and environmental safety.

Pollution pressure drives microbial assemblages that improve the phytoremediation potential of heavy metals by Ricinus communis.

Due to the rapid expansion of industrial activity, soil pollution has intensified. Plants growing in these polluted areas have developed a rhizobiome uniquely and specially adapted to thrive in such environments. However, it remains uncertain whether pollution acts as a sufficiently selective force to shape the rhizobiome, and whether these adaptations endure over time, potentially aiding in long-term phytoremediation. Therefore, in the present study, we aimed to compare whether the microbiome associated with roots from plants germinated in polluted riverbanks will improve the phytoremediation of Cd and Pb under mesocosm experiments compared with plants germinating in a greenhouse. The experimental design was a factorial 2 × 2, i.e., the origin of the plant and the presence or absence of 100 mg/L of Cd and 1000 mg/L of Pb. Our results showed that plants germinated in polluted riverbanks have the capacity to accumulate twice the amount of Pb and Cd during mesocosm experiments. The metagenomic analysis showed that plants from the river exposed to heavy metals at the end of mesocosm experiments were rich in Rhizobium sp. AC44/96 and Enterobacter sp. EA-1, Enterobacter soli, Pantoea rwandensis, Pantoea endophytica. In addition, those plants were uniquely associated with Rhizobium grahamii, which likely contributed to the differences in the levels of phytoremediation achieved. Furthermore, the functional analysis revealed an augmented functional potential related to hormones, metallothioneins, dismutases, and reductases; meanwhile, the plants germinated in the greenhouse showed an unspecific strategy to exceed heavy metal stress. In conclusion, pollution pressure drives stable microbial assemblages, which could be used in future phytostabilization and phytoremediation experiments.

Multivariate statistical analysis of bioavailability of heavy metals and mineral characterization in selected species of coastal flora.

This study presents a thorough investigation into the concentration of heavy metals and mineral composition within four distinct coastal flora species: Cyperus conglomeratus, Halopyrum mucronatum, Sericostem pauciflorum, and Salvadora persica. Employing rigorous statistical methodologies such as Pearson coefficient correlation, principal component analysis (PCA), analysis of variance (ANOVA), and interclass correlation (ICC), we aimed to elucidate the bioavailability of heavy metals, minerals, and relevant physical characteristics. The analysis focused on essential elements including copper (Cu), iron (Fe), manganese (Mn), zinc (Zn), magnesium (Mg2+), calcium (Ca2+), sodium (Na+), potassium (K+), and chloride (Cl-), all of which are known to play pivotal roles in the ecological dynamics of coastal ecosystems. Through PCA, we discerned distinctive patterns within PC1 to PC4, collectively explaining an impressive 99.65% of the variance observed in heavy metal composition across the studied flora species. These results underscore the profound influence of environmental factors on the mineral composition of coastal flora, offering critical insights into the ecological processes shaping these vital ecosystems. Furthermore, significant correlations among mineral contents in H. mucronatum; K+ with content of Na+ (r = 0.989) and Mg2+ (r = 0.984); as revealed by ICC analyses, contributed to a nuanced understanding of variations in electrical conductivity (EC), pH levels, and ash content among the diverse coastal flora species. By shedding light on heavy metal and mineral dynamics in coastal flora, this study not only advances our scientific understanding but also provides a foundation for the development of targeted environmental monitoring and management strategies aimed at promoting the ecological sustainability and resilience of coastal ecosystems in the face of ongoing environmental challenges.

Exposure to environmental pollutants selects for xenobiotic-degrading functions in the human gut microbiome.

Environmental pollutants from different chemical families may reach the gut microbiome, where they can be metabolized and transformed. However, how our gut symbionts respond to the exposure to environmental pollution is still underexplored. In this observational, cohort study, we aim to investigate the influence of environmental pollution on the gut microbiome composition and potential activity by shotgun metagenomics. We select as a case study a population living in a highly polluted area in Campania region (Southern Italy), proposed as an ideal field for exposomic studies and we compare the fecal microbiome of 359 subjects living in areas with high, medium and low environmental pollution. We highlight changes in gut microbiome composition and functionality that were driven by pollution exposure. Subjects from highly polluted areas show higher blood concentrations of dioxin and heavy metals, as well as an increase in microbial genes related to degradation and/or resistance to these molecules. Here we demonstrate the dramatic effect that environmental xenobiotics have on gut microbial communities, shaping their composition and boosting the selection of strains with degrading capacity. The gut microbiome can be considered as a pivotal player in the environment-health interaction that may contribute to detoxifying toxic compounds and should be taken into account when developing risk assessment models. The study was registered at ClinicalTrials.gov with the identifier NCT05976126.

Pervasive influence of heavy metals on metabolic pathways is potentially relieved by hesperidin to enhance the phytoremediation efficiency of Bassia scoparia.

Hesperidin (HSP), a flavonoid, is a potent antioxidant, metal chelator, mediator of signaling pathways, and regulator of metal uptake in plants. The study examined the ameliorative effects of HSP (100 µM) on Bassia scoparia grown under excessive levels of heavy metals (zinc (500 mg kg-1), copper (400 mg kg-1), cadmium (100 mg kg-1), and chromium (100 mg kg-1)). The study clarifies the underlying mechanisms by which HSP lessens metabolic mayhem to enhance metal stress tolerance and phytoremediation efficiency of Bassia scoparia. Plants manifested diminished growth because of a drop in chlorophyll content and nutrient acquisition, along with exacerbated deterioration of cellular membranes reflected in elevated reactive oxygen species (ROS) production, lipid peroxidation, and relative membrane permeability. Besides the colossal production of cytotoxic methylglyoxal, the activity of lipoxygenase was also higher in plants under metal toxicity. Conversely, hesperidin suppressed the production of cytotoxic ROS and methylglyoxal. Hesperidin improved oxidative defense that protected membrane integrity. Hesperidin caused a more significant accumulation of osmolytes, non-protein thiols, and phytochelatins, thereby rendering metal ions non-toxic. Hydrogen sulfide and nitric oxide endogenous levels were intricately maintained higher in plants treated with HSP. Hesperidin increased metal accumulation in Bassia scoparia and thereby had the potential to promote the reclamation of metal-contaminated soils.

An activatable fluorescence probe for rapid detection and in situ imaging of ß-galactosidase activity in cabbage roots under heavy metal stress.

ß-Galactosidase (ß-gal), an enzyme related to cell wall degradation, plays an important role in regulating cell wall metabolism and reconstruction. However, activatable fluorescence probes for the detection and imaging of ß-gal fluctuations in plants have been less exploited. Herein, we report an activatable fluorescent probe based on intramolecular charge transfer (ICT), benzothiazole coumarin-bearing ß-galactoside (BC-ßgal), to achieve distinct in situ imaging of ß-gal in plant cells. It exhibits high sensitivity and selectivity to ß-gal with a fast response (8 min). BC-ßgal can be used to efficiently detect the alternations of intracellular ß-gal levels in cabbage root cells with considerable imaging integrity and imaging contrast. Significantly, BC-ßgal can assess ß-gal activity in cabbage roots under heavy metal stress (Cd2+, Cu2+, and Pb2+), revealing that ß-gal activity is negatively correlated with the severity of heavy metal stress. Our work thus facilitates the study of ß-gal biological mechanisms.

Selection of pollution-safe head cabbage: Interaction of multiple heavy metals in soil on bioaccumulation and transfer.

Screening for pollution-safe cultivars (PSCs) is a cost-effective strategy for reducing health risks of crops in heavy metal (HM)-contaminated soils. In this study, 13 head cabbages were grown in multi-HMs contaminated soil, and their accumulation characteristics, interaction of HM types, and health risks assessment using Monte Carlo simulation were examined. Results showed that the edible part of head cabbage is susceptible to HM contamination, with 84.62% of varieties polluted. The average bio-concentration ability of HMs in head cabbage was Cd> > Hg > Cr > As>Pb. Among five HMs, Cd and As contributed more to potential health risks (accounting for 20.8%-48.5%). Significant positive correlations were observed between HM accumulation and co-occurring HMs in soil. Genotypic variations in HM accumulation suggested the potential for reducing health risks through crop screening. G7 is a recommended variety for head cabbage cultivation in areas with multiple HM contamination, while G3 could serve as a suitable alternative for heavily Hg-contaminated soils.

Potential strategies for phytoremediation of heavy metals from wastewater with circular bioeconomy approach.

Water pollution is an inextricable problem that stems from natural and human-related factors. Unfortunately, with rapid industrialization, the problem has escalated to alarming levels. The pollutants that contribute to water pollution include heavy metals (HMs), chemicals, pesticides, pharmaceuticals, and other industrial byproducts. Numerous methods are used for treating HMs in wastewater, like ion exchange, membrane filtration, chemical precipitation, adsorption, and electrochemical treatment. But the remediation through the plant, i.e., phytoremediation is the most sustainable approach to remove the contaminants from wastewater. Aquatic plants illustrate the capacity to absorb excess pollutants including organic and inorganic compounds, HMs, and pharmaceutical residues present in agricultural, residential, and industrial discharges. The extensive exploitation of these hyperaccumulator plants can be attributed to their abundance, invasive mechanisms, potential for bioaccumulation, and biomass production. Post-phytoremediation, plant biomass can be toxic to both water bodies and soil. Therefore, the circular bioeconomy approach can be applied to reuse and repurpose the toxic plant biomass into different circular bioeconomy byproducts such as biochar, biogas, bioethanol, and biodiesel is essential. In this regard, the current review highlights the potential strategies for the phytoremediation of HMs in wastewater and various strategies to efficiently reuse metal-enriched biomass material and produce commercially valuable products. The implementation of circular bioeconomy practices can help overcome significant obstacles and build a new platform for an eco-friendlier lifestyle.

ABA-importing transporter (AIT1) synergies enhances exogenous ABA minimize heavy metals accumulations in Arabidopsis.

Exogenous abscisic acid (ABA) presents a novel approach to mitigate heavy metal (HM) accumulation in plants, yet its efficacy against multiple HMs and potential enhancement methods remain underexplored. In this study, we demonstrated that the exogenous ABA application simultaneously decreased Zn, Cd and Ni accumulation by 22-25 %, 27-39 % and 60-62 %, respectively, in wild-type (WT) Arabidopsis. Conversely, ABA reduced Pb in shoots but increased its root concentration. ABA application also modulated the expression of HM uptake genes, inhibiting IRT1, NRAMP1, NRAMP4, and HMA3, and increasing ZIP1 and ZIP4 expressions. Further analysis revealed that overexpressing the ABA-importing transporter (AIT1) in plants intensified the reduction of Cd, Zn, and Ni, compared to WT. However, the inhibitory effect of exogenous ABA on Pb accumulation was mitigated in shoots with higher AIT1 expression. Furthermore, HMs-induced growth inhibition and the damage to photosynthesis were also alleviated with ABA treatment. Conclusively, AIT1's synergistic effect with ABA effectively reduces Cd, Zn and Ni accumulation, offering a synergistic approach to mitigate HM stress in plants.

Metal bioaccumulation in marine invertebrates and risk assessment in sediments from South African coastal harbours and natural rocky shores.

Industrial and urban activities are major contributors to metal contamination in coastal systems, often impacting the physiology, distribution and diversity of marine invertebrates. This study assessed metal contaminations in sediments, seawater, algae and invertebrates across four armoured systems (harbours) and two natural sites along the south coast of South Africa. Bioaccumulation factors such as Biosediment (BSAF), Biowater (BWAF), Bioaccumulation (BAF) and bioremediation of metals by invertebrate bioindicators were also determined. Spatial variation in metal concentrations were observed, however, bioaccumulation of metals was site and species-specific. Invertebrates bioaccumulated higher metal concentrations in armoured than natural sites, with filter feeders exhibiting higher concentrations than grazers. Among filter feeders, Octomeris angulosa and Crassostrea gigas bioaccumulated elevated aluminium (Al), arsenic (As), chromium (Cr), zinc (Zn) and copper (Cu), while, Perna perna accumulated elevated nickel (Ni), cadmium (Cd) and lead (Pb). Among grazers, Siphonaria serrata and Scutellastra longicosta bioaccumulated elevated Al, Cr, Cd, cobalt (Co), Cu, Ni and Zn. Bioaccumulation factors indicated that (As, Ni, Zn) were bioaccumulated by algae, and invertebrates from sediment (BSAF>1) and from seawater (BWAF>1). Additionally, invertebrates bioaccumulated metals from their prey item, algae as indicated by (BAF>1). Arsenic Cd and Pb in invertebrates were above the maximum limit set for human consumption by various regulatory bodies. Our findings underscore the significant role of coastal invertebrates in bioaccumulating and bioremediating metals, suggesting a natural mechanism for water quality enhancement, especially in urbanised coastal areas.

Effects of nitrogen regulation on heavy metal phytoextraction efficiency (Leucaena leucocephala): Application of a nitrogen fertilizer and a fungal agent.

Lead (Pb) and cadmium (Cd) have been identified as the primary contaminants in soil, posing potential health threats. This study aimed to examine the effects of applying a nitrogen fertilizer and a fungal agent Trichoderma harzianum J2 (nitrogen alone, fungi alone, and combined use) on the phytoremediation of soils co-contaminated with Pb and Cd. The growth of Leucaena leucocephala was monitored in the seedling, differentiation, and maturity stages to fully comprehend the remediation mechanisms. In the maturity stage, the biomass of L. leucocephala significantly increased by 18% and 29% under nitrogen-alone (NCK+) and fungal agent-alone treatments (J2), respectively, compared with the control in contaminated soil (CK+). The remediation factors of Pb and Cd with NCK+ treatment significantly increased by 50% and 125%, respectively, while those with J2 treatment increased by 73% and 145%, respectively. The partial least squares path model suggested that the nitrogen-related soil properties were prominent factors affecting phytoextraction compared with biotic factors (microbial diversity and plant growth). This model explained 2.56 of the variation in Cd concentration under J2 treatment, and 2.97 and 2.82 of the variation in Pb concentration under NCK+ and J2 treatments, respectively. The redundancy analysis showed that the samples under NCK+ and J2 treatments were clustered similarly in all growth stages. Also, Chytridiomycota, Mucoromucota, and Ciliophora were the key bioindicators for coping with heavy metals. Overall, a similar remediation mechanism allowed T. harzianum J2 to replace the nitrogen fertilizer to avoid secondary pollution. In addition, their combined use further increased the remediation efficiency.

Contrasting plant-induced changes in heavy metals dynamics: Implications for phytoremediation strategies in estuarine wetlands.

Wetland plants play a crucial role in regulating soil geochemistry, influencing heavy metal (HM) speciation, bioavailability, and uptake, thus impacting phytoremediation potential. We hypothesized that variations in HM biogeochemistry within estuarine soils are controlled by distinct estuarine plant species. We evaluated the soils (pH, redox potential, rhizosphere pH, HM total concentration, and geochemical fractionation), plant parts (shoot and root), and iron plaques of three plants growing in an estuary affected by Fe-rich mine tailings. Though the integration of multiple plant and soil analysis, this work emphasizes the importance of considering geochemical pools of HM for predicting their fate. Apart from the predominance of HM associated with Fe oxides, Typha domingensis accumulated the highest Cr and Ni contents in their shoots (> 100 mg kg-1). In contrast, Hibiscus tiliaceus accumulated more Cu and Pb in their roots (> 50 mg kg-1). The differences in rhizosphere soil conditions and root bioturbation explained the different potentials between the plants by altering the soil dynamics and HM's bioavailability, ultimately affecting their uptake. This study suggests that Eleocharis acutangula is not suitable for phytoextraction or phytostabilization, whereas Typha domingensis shows potential for Cr and Ni phytoextraction. In addition, we first showed Hibiscus tiliaceus as a promising wood species for Cu and Pb phytostabilization.

Role of Histidine 310 in Amydetes vivianii firefly luciferase pH and metal sensitivities and improvement of its color tuning properties.

Firefly luciferases emit yellow-green light and are pH-sensitive, changing the bioluminescence color to red in the presence of heavy metals, acidic pH and high temperatures. These pH and metal-sensitivities have been recently harnessed for intracellular pH indication and toxic metal biosensing. However, whereas the structure of the pH sensor and the metal binding site, which consists mainly of two salt bridges that close the active site (E311/R337 and H310/E354), has been identified, the specific role of residue H310 in pH and metal sensing is still under debate. The Amydetes vivianii firefly luciferase has one of the lowest pH sensitivities among the group of pH-sensitive firefly luciferases, displaying high bioluminescent activity and special spectral selectivity for cadmium and mercury, which makes it a promising analytical reagent. Using site-directed mutagenesis, we have investigated in detail the role of residue H310 on pH and metal sensitivity in this luciferase. Negatively charged residues at position 310 increase the pH sensitivity and metal sensitivity; H310G considerably increases the size of the cavity, severely impacting the activity, H310R closes the cavity, and H310F considerably decreases both pH and metal sensitivities. However, no substitution completely abolished pH and metal sensitivities. The results indicate that the presence of negatively charged and basic side chains at position 310 is important for pH sensitivity and metals coordination, but not essential, indicating that the remaining side chains of E311 and E354 may still coordinate some metals in this site. Furthermore, a metal binding site search predicted that H310 mutations decrease the affinity mainly for Zn, Ni and Hg but less for Cd, and revealed the possible existence of additional binding sites for Zn, Ni and Hg.

Bioaccumulation and transferreing for impacts on Cd and Pb by aphid consumption of the broad bean, Vicia faba L, in soil heavy metal pollution.

Heavy metal pollution threatens human and ecological health. Heavy metals can exist in the soil for a long time and migrate to organisms along the food chain. However, only a few studies have investigated the effects of a single stress on broad beans. Here, we aimed to characterize Cd and Pb bioaccumulation, at varying concentrations, in the broad bean, Vicia faba L. We also determined how the bioaccumulated metals are impacted by aphids that consume the plant. No significant difference was noted in the germination rates of broad beans at the early stage of planting (after 8 days), but eventually, the germination rates of broad beans at all time points first decreased and then increased, and the highest inhibition efficiency was observed in the T3 group (12.5 mg/L Cd2+ + 50 mg/L Pb2+). Fourteen days after planting, there was no significant difference in seedling height between the T5 (50 mg/L Cd2+ + 200 mg/L Pb2+) and control groups; however, that in the other groups decreased significantly and there was no dependence between stress concentration and inhibition efficiency. In addition, both Cd and Pb in the soil could be transferred to broad beans, and the concentration of Pb in the roots of broad beans was greater than that of Cd, whereas the opposite was observed in the stems and leaves. Notably, under mixed stress, aphids could significantly reduce the content of Cd in broad beans; similarly, the Pb content in the roots and stems of broad beans decreased significantly after being infested with aphids but increased significantly in the leaves. Further, the aphid infestation decreased the Pb content in the soil and the soil Cd content in the highest concentration group (T5 group) (50 mg/L Cd2+ + 200 mg/L Pb2+). These results highlight the necessity of focusing on the effect of insects on heavy metal remediation in plants and provide a new perspective for reducing plant Cd toxicity.

Modified diatomite for soil remediation and its implications for heavy metal absorption in Calendula officinalis.

BACKGROUND: Among different adsorbents, natural and inorganic compounds such as diatomite are important and advantageous in terms of high efficiency and cost-effectiveness, and function in stabilizing heavy metals in the environment. Calendula officinalis, a plant known as a high accumulator of heavy metals, was cultivated in soil treated with varying concentrations of modified diatomite to demonstrate the efficiency of modified diatomite in stabilizating of heavy metals in soils, RESULTS: The modification of diatomite aimed to enhance Calendula officinalis adsorptive properties, particularly towards heavy metals such as lead (Pb), Zinc (Zn), Chromium (Cr), Nickle (Ni), and Copper (Cu), common contaminants in industrial soils. The experimental design included both control and treated soil samples, with assessments at regular intervals. Modified diatomite significantly decreased the bioaccumulation of heavy metals in contaminated soils except Zn, evidenced by decreased DTPA extractable heavy metals in soil and also heavy metal concentrations in plant tissues. Using 10% modified diatomite decreased 91% Pb and Cu, 78% Cr, and 79% Ni concentration of plants compared to the control treatment. The highest concentration of Zn in plant tissue was observed in 2.5% modified diatomite treatment. Remarkably, the application of modified diatomite also appeared to improve the nutrient profile of the soil, leading to enhanced uptake of key nutrients like phosphorus (P) 1.18%, and potassium (K) 79.6% in shoots and 82.3% in roots in Calendula officinalis. Consequently, treated plants exhibited improved growth characteristics, including shoots and roots height of 16.98% and 12.8% respectively, and shoots fresh and dry weight of 48.5% and 50.2% respectively., compared to those in untreated, contaminated soil. CONCLUSION: The findings suggest promising implications for using such amendments in ecological restoration and sustainable agriculture, particularly in areas impacted by industrial pollution.

Phenotypic characterization for bioremediation suitability of isolates from Southern Tunisian tannery effluent.

Effluents from the leather tanning industry contain diverse pollutants, including hazardous heavy metals, posing threats to public health and the surrounding environment. Indigenous bacterial isolates can represent an eco-friendly approach for tannery wastewater treatment; however, phenotypic characterization is necessary to determine whether these strains are suitable for bioremediation. In the present study, we analyzed seven new Enterococcus faecium strains and two new Bacillus subtillis strains isolated from effluents from the Southern Tunisian Tannery (ESTT). We evaluated phenotypic features beneficial for bioremediation, including biofilm formation, hydrophobicity, and exoenzyme activities. Additionally, we examined characteristics naturally occurring in environmental bacteria but less desirable in strains selected for bioremediation, such as antibiotic resistances and pathogenicity indicators. The observed phenotypes were then compared with whole-genome analysis. We observed biofilm production in two slime-producing bacteria, B. licheniformis RLT6, and E. faecium RLT8. Hydrophobicity of E. faecium strains RLT1, RLT5, RLT8, and RLT9, as well as B. licheniformis RLT6 correlated positively with increasing ESTT concentration. Exoenzyme activities were detected in E. faecium strains RLT2, RLT4, and RLT7, as well as B. licheniformis RLT6. As anticipated, all strains exhibited common resistances to antibiotics and hemolysis, which are widespread in nature and do not hinder their application for bioremediation. Importantly, none of the strains exhibited the pathogenic hypermucoviscosity phenotype. To the best of our knowledge, this is the first report consolidating all these phenotypic characteristics concurrently, providing a complete overview of strains suitability for bioremediation. IMPORTANCE: The study evaluates the bioremediation potential of seven Enterococcus faecium strains and two Bacillus subtillis strains isolated from the effluents from the Southern Tunisian tannery (ESTT), which pose threats to public health and environmental integrity. The analysis primarily examines the phenotypic traits crucial to bioremediation, including biofilm formation, hydrophobicity, and exoenzyme activities, as well as characteristics naturally occurring in environmental bacteria related to heavy metal resistance, such as antibiotic resistances. Several strains were found to have high bioremediation potential and exhibit only antibiotic resistances commonly found in nature, ensuring their application for bioremediation remains uncompromised. The results of the exhaustive phenotypic analysis are contrasted with the whole genome sequences of the nine strains, underscoring the appropriateness of these bacterial strains for eco-friendly interventions in tannery wastewater treatment.

Bioaccumulation and biological effects of hydrogenated cement particles in the marine bivalve, Mytilusgalloprovincialis.

The decommissioning and normal functioning of nuclear facilities can result in the production and release of airborne particles in the environment. Aquatic biota are expected to be exposed to these particles considering that nuclear facilities are often located near water bodies. Aerosols, such as cement dust, can interact with radionuclides as well as with heavy metals, and therefore elicit not only radiological impacts but also chemical toxicity. In the present study, we aimed to determine the effects of hydrogenated cement particles (HCPs) as a first step before evaluating any radiotoxicity of tritiated cement particles in the marine mussels, Mytilus galloprovincialis. Responses at different levels of biological organisation were assessed, including clearance rate (CR), tissue specific accumulation, DNA damage and transcriptional expression of key stress related genes. Acute (5 h) and medium-term, chronic (11 d) exposures to 1000 µg L-1 HCPs showed that bioaccumulation, assessed using Cu as a proxy and determined by inductively coupled plasma mass spectrometry, was time and tissue dependent. The highest levels of Cu were found in the digestive gland (DG) after 11 d. HCP exposure caused changes in the expression of oxidative and other stress-related genes, including mt20 in DG and gst and sod in the gill after 5 h exposure, while an overexpression of hsp70 in the gill was observed after 11 d. Genotoxic effects in haemocytes were observed after 11 d of HCP exposure. Multivariate analysis indicated that oxidative stress is the most probable factor contributing to overall physiological dysfunction. Our results provide a baseline to perform further studies employing tritiated cement particles. Specifically, future work should focus on the DG since only this tissue showed significant bioaccumulation when compared to the negative control.