High Metal Tolerance Research Articles

Biotechnological approaches for enhancement of heavy metal phytoremediation capacity of plants.

Heavy metals are extremely hazardous for human health due to their toxic effects. They are non-biodegradable in nature, thus remain in the environment and enter and accumulate in the human body through biomagnification; hence, there is a serious need of their remediation. Phytoremediation has emerged as a green, sustainable, and effective solution for heavy metal removal and many plant species could be employed for this purpose. Plants are able to sequester substantial quantity of heavy metals, in some cases thousands of ppm, due to their robust physiology enabling high metal tolerance and anatomy supporting metal ion accumulation. Identification and modification of potential target genes involved in heavy metal accumulation have led to improved phytoremediation capacity of plants at the molecular level. The introduction of foreign genes through genetic engineering approaches has further enhanced phytoremediation capacity manifolds. This review gives an insight towards improving the phytoremediation efficiency through a better understanding of molecular mechanisms involved, expression of different proteins, genetic engineering approaches for transgenic production, and genetic modifications. It also comprehends novel omics tools such as genomics, metabolomics, proteomics, transcriptomics, and genome editing technologies for improvement of phytoremediation ability of plants.

Bacterial and microalgal co-fixation for remediation of industrial wastewater contaminated with arsenic, mercury, and other pollutants

Microbial remediation is an efficient approach for improving heavy metal-contaminated water environments. Herein, this article developed a composite bacterial agent (CBA) with a high heavy metal tolerance. Within 12 h, the CBA demonstrated removal efficiencies of 65.18 ± 1.53% for As and 60.73 ± 0.94% for Hg in wastewater. This study prepared bacterial–algal fixed spheres (BAFS) to further enhance the removal efficiencies of As and Hg. Moreover, during desorption using 0.1 mol/L HNO3 for 60 min, the BAFS maintained high removal efficiencies for As and Hg after five adsorption–desorption cycles. Applying BAFS to industrial wastewater collected from factory outfall caused substantial reductions in chemical pollutants and other heavy metals. Scanning electron microscopy analysis further revealed that the internal cavities formed through the crosslinking of immobilized materials provided excellent survival carriers for bacteria and microalgae. Infrared spectroscopy analysis demonstrated the involvement of three functional groups, namely -OH, -CH2-, and C-O-C, in pollutant adsorption. Additionally, microbial community diversity analysis indicated that immobilization effectively preserved the pollutant adsorption ability of the microorganisms, increasing the abundance of functional microbial populations. These characteristics improved the efficiency of industrial wastewater treatment while promoting recycling.

Potential of Plant Based Metallophytes for Phytoremediation in Agriculture

Metallophytes are the unique group of plants that have evolved to thrive in metal rich environments and have drawn plenty of attention. Remediating heavy metal contaminated places with plants is an effective choice due to phytoremediation, an environmentally friendly method that uses plants to mitigate the pollution. Metallophytes are ideal options for phytoremediation applications due to their inherent traits such as hyper-accumulation, efficient metal absorption and tolerance mechanisms impacting both the plant and soil. These plants absorb and translocate heavy metals, detoxifying the soil while accumulating them in tissues. This reduces metal toxicity in soil and holds potential for resources recovery. The role of metallophytes in phytoremediation is analysed in this review with particular focus given to their ways of metal absorption, translocation and detoxification. Metallophytes have high metal tolerance and accumulation capacities due to their unique physiological and biochemical adaptations including enhanced metal sequestration in vacuoles, metal chelation by phytochelatins and activation of anti-oxidant defence systems. This review also highlights the significance of metallophytes in enhancing the soil health, reducing metal bioavailability, and promoting the ecological sustainability as well as their potential for restoring contaminated ecosystems. Utilizing the unique capabilities of metallophytes obtained from plants possesses enormous possibilities to minimise the negative effects of heavy metal pollution, protect ecosystems, and promote sustainable development for future generations. Eventually, it outlines future research approaches that aim to enhance metallophytes based phytoremediation strategies, widen their implementation and include them in holistic approaches for environmental restoration and sustainable land management.

Prevalence of diverse antimicrobial resistance genes and bacteria in sewage treatment plant-derived sludge environment.

Antimicrobial resistance (AMR) contamination in the environment is one of the most significant worldwide threats of the 21st century. Since sludge is heavily exposed to diverse contaminants, including pharmaceuticals, the inhabitant bacterial population is expected to exhibit resistance to antimicrobial agents. In this study, sewage treatment plant (STP) sludge samples were analyzed to assess the antibiotic-resistant bacterial population, abundance of AMR genes (ermF, qnrS, Sul1, blaGES, blaCTX-M, and blaNDM), and mobile genetic elements (intl1 and IS26). Out of 16, six bacterial isolates exhibited resistance to 13 antibiotics with a high multiple antibiotic resistance index (MARI) (0.93) and high metal tolerance. Quantitative polymerase chain reaction showed the abundance of target genes ranging from 6.6×103 to 6.5×108 copies g-1 sludge. The overall outcome reveals that STP sludge comprised varied multidrug-resistant bacterial populations. It will give insights into the functions of heavy metals and biofilm development in the selection and spread of AMR genes and the associated bacteria. Therefore, the application of sludge needs proper screening for AMR and metal contamination prior to its countless applications. This study will contribute immensely to the risk analysis of STP effluents on environmental health, including control of AMR transmission.

Exploring microbial adaptation of immobilised acidophilic cultures to improve microbial oxidation rates and copper tolerance in e-waste bioleaching

The rate of ferric iron regeneration by microbial oxidation is the rate determining step in the bioleaching of printed circuit boards (PCBs). Therefore, improvement of the volumetric rate of ferric iron formation is key for the overall bioleaching efficiency. The volumetric rate is impacted by both the specific rate and the biomass concentration. Limiting the exposure of the bioleaching microorganisms to accumulated toxic metal ions in solution, as well as the presence of inhibiting material components in PCBs through biofilm formation and immobilisation, as well as their adaptation to these inhibitors, is proposed to mitigate against decrease in specific rate while biomass retention by immobilisation is expected to positively impact volumetric rate. In this study, a mixed mesophilic culture, consisting of Leptospirillum (L.) ferriphilum, Acidithiobacillus (At.) caldus, Acidiplasma (Ap.) cupricumulans as dominant species was immobilised on polyurethane foam (PUF) and adapted to 6.0 g/L Cu2+. The rate of microbial ferrous iron oxidation by the immobilised culture was compared to that of planktonic cultures. Further, the performance of both the planktonic and immobilised Cu-adapted cultures (6.0 g/L of Cu2+) were compared with non-adapted planktonic and immobilised cells in the presence of increasing Cu2+ concentrations (0–50 g/L Cu2+).Both the Cu-adapted planktonic cells and the non-adapted immobilised cells demonstrated improved tolerance to Cu2+ stress relative to non-adapted planktonic cells. The Cu-adapted planktonic cells showed higher volumetric ferrous iron oxidation rates (0.0359 ± 0.0023 g Fe2+.L−1.h−1 at 22 g/L Cu2+) than the non-adapted immobilised cells (0.0331 ± 0.0021 g Fe2+.L−1.h−1) in the presence of Cu2+ concentrations exceeding 6 g/L. The Cu-adapted immobilised cells exhibited higher tolerance to Cu2+ stress and higher oxidation kinetics (0.0622 ± 0.0064 g Fe2+.L−1.h−1) than the Cu-adapted planktonic and non-adapted immobilised cells. This study provides a novel approach for improving culture performance and minimising the inhibitory effect of Cu2+ ion on L. ferriphilum dominated cultures. High microbial activity and metal tolerance of Cu-adapted immobilised cells presents an opportunity for immobilised microbial systems to be used both in bioleaching of e-waste streams, such as PCBs, and in bioleaching of mineral concentrates, ores and wastes with Cu2+-rich leachates.

Phytoremediation ability and selected genetic transcription in Hydrocotyle umbellata-under cadmium stress

Cadmium (Cd) is the most toxic element which may cause serious consequences to microbial communities, animals, and plants. The use of green technologies like phytoremediation employs plants with high biomass and metal tolerance to extract toxic metals from their rooting zones. In the present work, Hydrocotyle umbellata was exposed to five Cd concentrations (2, 4, 6, 8, and 10 µmol) in triplicates to judge its phytoextraction ability. Effects of metal exposure on chlorophyll (Chl), bio-concentration factor (BCF), translocation factor (TF), and electrolyte leakage (EL) were analyzed after 10 days of treatment. Metal-responding genes were also observed through transcriptomic analysis. Roots were the primary organs for cadmium accumulation followed by stolon and leaves. There was an increase in EL. Plants showed various symptoms under increasing metal stress namely, chlorosis, browning of the leaf margins, burn-like areas on the leaves, and stunted growth, suggesting a positive relationship between EL, and programmed cell death (PCD). Metal-responsive genes, including glutathione, expansin, and cystatin were equally expressed. The phytoextraction capacity and adaptability of H. umbellata L. against Cd metal stress was also demonstrated by BCF more than 1 and TF less than 1.

Lead biosorption profiling of endophytic Aspergillus flavus SGE34 isolated from Cleome viscosa Linn.

ABSTRACT Lead is an environmental pollutant that causes remarkable damage to various organs in the human body, especially the nervous system. Removal of lead by conventional methods is costly, and therefore, in the current scenario, biosorption using fungi is extensively explored as they provide good metal uptake systems. The present study evaluated the Pb (II) biosorption potential of endophytic fungi Aspergillus flavus SGE34. The fungal isolate was obtained from the root of an indigenous medicinal plant of the Chhattisgarh region named Cleome viscosa Linn. The biosorption potential of dead fungal biomass was optimized at different operating parameters like contact time, pH, and temperature. The maximum biosorption values were found at pH 6.0 with an equilibrium time of 150 minutes at 350C. The Fourier transform infrared spectroscopy study revealed that the pattern of new absorption bands, altered absorption intensity, and shift in wavenumber of functional groups was deduced, due to interaction between metal ions and active sites of biosorbent. The present study concluded that A. flavus SGE34 has high metal tolerance and biosorption capacity; it could effectively remove lead from industrial effluents.

Aspergillus luchuensis, an Endophyte Fungus from the Metal Hyperaccumulator Plant Prosopis laevigata, Promotes Its Growth and Increases Metal Translocation

Heavy metal pollution is a worldwide environmental and human health problem. Prosopis laevigata is a hyperaccumulator legume that bioaccumulates Pb, Cu and Zn. With interest in designing phytoremediation strategies for sites contaminated with heavy metals, we isolated and characterized endophytic fungi from the roots of P. laevigata growing on mine tailings located in Morelos, Mexico. Ten endophytic isolates were selected by morphological discrimination and a preliminary minimum inhibitory concentration was determined for zinc, lead and copper. A novel strain of Aspergillus closest to Aspergillus luchuensis was determined to be a metallophile and presented a marked tolerance to high concentrations of Cu, Zn and Pb, so it was further investigated for removal of metals and promotion of plant growth under greenhouse conditions. The control substrate with fungi promoted larger size characters in P. laevigata individuals in comparison with the other treatments, demonstrating that A. luchuensis strain C7 is a growth-promoting agent for P. laevigata individuals. The fungus favors the translocation of metals from roots to leaves in P. laevigata, promoting an increased Cu translocation. This new A. luchuensis strain showed endophytic character and plant growth-promotion activity, high metal tolerance, and an ability to increase copper translocation. We propose it as a novel, effective and sustainable bioremediation strategy for copper-polluted soils.

Identification and Characterization of Aluminium Tolerant Bacteria Isolated from Soil Contaminated by Electroplating and Automobile Waste

Due to anthropogenic activities and the advancement of industries, metal contamination is growing globally. Aluminum toxicity is seriously endangering plants, animals, and humans by rapidly rising in soil and water. Even though some fungi can tolerate aluminum, researchers are interested in finding bacteria that are resistant to aluminum. The current state of knowledge on bacteria resistant to aluminum is extremely limited. In the present study, bacterial isolates from soil near a metal electroplating and automobile industry in Punjab, India, were isolated and then screened for high aluminum metal tolerance. The aluminum tolerant bacterial isolate was identified as Cedecea davisae M1, a member of the Enterobacteriaceae family, using morphological, biochemical, and 16srRNA gene sequence analyses. The spectroscopic results indicate that the strain may tolerate up to 150 ppm of aluminum. Antibiotic resistance of Cedecea davisae M1 was determined using disks on Luria agar plates, and the bacteria were found to be resistant to vancomycin, ampicillin, carbenicillin, and rifampicin. The findings of the study indicated that the strain might be able to remove aluminum toxicity from the environment, which needs to be further explored.

Foliar application of lanthanum promotes growth and phytoremediation potential Solanum nigrum L

The hormetic effect of rare earth elements (REEs) has been found in a variety of crops and has been promoting crop growth for decades. Spraying leaves with REEs can enhance the endocytosis of plant roots. The non-selectivity of endocytosis is conducive to the direct absorption of environmental pollutants. The hyperaccumulator Solanum nigrum L. (S. nigrum), as a plant with high biomass and heavy metal tolerance, is a good candidate for phytoremediation. La(III), as a typical light REE, also has an obvious hormetic effect on S. nigrum. At 10 μM La(III), the biomass of S. nigrum reached the maximum, which was 89% greater than the control, and La(III) concentration was much lower than the previously reported optimum of 56 μM for general plants. In the present study, enhanced endocytosis after foliar spraying of La(III) was firstly observed in the root cell of hyperaccumulation plants, and La(III) increased the biomass of S. nigrum by improving the photosynthetic system, and promoting nutrient uptake and root development. The antioxidant defense system improved by La(III) contributed to the tolerance of S. nigrum to heavy metals. Applying a reasonable range of La(III) is beneficial to improving S. nigrum growth and tolerance of heavy metals. Compared with spraying deionized water, the translocation factor and bioaccumulation factor value of S. nigrum to cadmium increased by 15% and 21% respectively when spraying 10 μM La(III). Our findings provide a reference for improving hyperaccumulator plant growth and biomass, which improves phytoremediation efficiency.

Isolation of heavy metal-resistant Staphylococcus epidermidis strain TWSL_22 and evaluation of heavy metal bioremediation potential of recombinant E. coli cloned with isolated cadD.

A heavy metal-resistant bacterial strain, TWSL_22 was isolated from an industrial effluent sample and tested for heavy metal tolerance and resistance. The strain was molecularly characterized as Staphylococcus epidermidis based on 16S rDNA gene analysis and the sequence was deposited in the NCBI repository (accession number KT184893.1). Metal removal activity (P<.001) of TWSL_22 was 99.99±0.001%, 74.43±2.51%, and 51.16±4.17% for Cd, Pb, and Cu, respectively. Highest MIC was observed for Cd. Antibiotic susceptibility assays revealed the strain TWSL_22 to be resistant to several antibiotics. The strain was screened for possible heavy metal-resistant genes and presence of cadA, copA, and cadD was confirmed by PCR. A DNA fragment containing complete sequence of cadD (618bp) was isolated and cloned into pET 21a(+), transformed into E. coli BL21 and designated as E. coli/cadDET. E. coli/cadDET showed high metal tolerance capacity and could remove over 82% of heavy metals (Zn2+, Cd2+, Cu2+, and Cr3+) in the industrial effluent.

Cadmium Uptake From Soil by Ornamental Metallophytes: A Meta-analytical Approach.

Soil pollution by cadmium (Cd) is a serious issue worldwide affecting environmental and human health. Conventional chemical and physical methods of treating contaminated soil are costly, time-consuming, and less effective. Phytoremediation using ornamental plants is a safe and effective method for the treatment of heavy metal-polluted soil due to their rapid growth and accumulation of biomass, high heavy metal tolerance, and non-edible nature. The present study is the first attempt for the meta-analysis of existing literature on Cd accumulation and translocation by ornamental plants. The uptake and transfer capacity of ornamental plants was measured using the bio-concentration factor (BCF) and translocation factor (TF). The results indicate that ornamental plants have varying Cd-absorption capacities. Among the 49 plant species identified from 31 articles, Helianthus annuus (BCF = 5.785), Impatiens glandulifera (BCF = 4.722), and Crassocephalum crepidioides (BCF = 3.623) represented higher accumulation capacity, whereas Rorippa globosa (TF = 1.653) and Sedum spectabile Boreau (TF = 1.579) represented significantly higher translocation capacity for Cd. The contribution of various environmental factors in influencing BCF was obtained through multiple linear regression analysis. Results showed that soil pH was the major factor influencing the BCF. To further explain the influence of four main factors that are soil pH, soil organic matter (SOM), cation exchange capacity (CEC), and soil Cd concentration on the accumulation efficiency of ornamental plants, a subgroup meta-analysis was performed. Results of the subgroup meta-analysis revealed that the BCF is negatively correlated with the soil pH and SOM, while the estimated limit of soil Cd concentration for growing ornamental plants was up to 50 mg/kg. Results of this study indicate that choosing a native hyperaccumulator is not the sole key to the success of a phytoremediation design, rather the conditions of the pedosphere will determine the regulating factor for efficient removal. In order to overcome the issue of recirculation and gradual release in the rhizosphere, it is important to match the type of hyperaccumulators to the soil environment (pH, CEC, SOM, etc.) to achieve maximum translocation and desired removal. This study will help researchers to pair the right plant with environmental conditions and customize more efficient phytoremediation systems.

Examination of the Metallothionein Gene Family in Greater Duckweed Spirodela polyrhiza.

Duckweeds are aquatic plants that proliferate rapidly in a wide range of freshwaters, and they are regarded as a potential source of sustainable biomass for various applications and the cost-effective bioremediation of heavy metal pollutants. To understand the cellular and molecular basis that underlies the high metal tolerance and accumulation capacity of duckweeds, we examined the forms and transcript profiles of the metallothionein (MT) gene family in the model duckweed Spirodela polyrhiza, whose genome has been completely sequenced. Four S. polyrhiza MT-like genes were identified and annotated as SpMT2a, SpMT2b, SpMT3, and SpMT4. All except SpMT2b showed high sequence homology including the conserved cysteine residues with the previously described MTs from flowering plants. The S. polyrhiza genome appears to lack the root-specific Type 1 MT. The transcripts of SpMT2a, SpMT2b, and SpMT3 could be detected in the vegetative whole-plant tissues. The transcript abundance of SpMT2a was upregulated several-fold in response to cadmium stress, and the heterologous expression of SpMT2a conferred copper and cadmium tolerance to the metal-sensitive ∆cup1 strain of Saccharomyces cerevisiae. Based on these results, we proposed that SpMT2a may play an important role in the metal detoxification mechanism of duckweed.

Beneficial effects of cadmium on plant defense of an invasive plant

Soil contamination by heavy metals is widespread as an inevitable consequence of every-increasing industrial and mining activities. In contaminated habitats, many sensitive plant species may extinct, and a few species, specifically the invasive plants with higher metal tolerance, can survive or colonize in such empty niche. The accumulation of heavy metals in plant tissues is one of the defense strategies against pathogens and herbivores. However, little is known regarding whether increased metal content is beneficial to the defense of invasive plants when competing with native plants. In this study, we explored the foliar chemistry of invasive alligator weed, Alternanthera philoxeroides , and its native congener sessile joyweed, A. sessilis , in response to cadmium (Cd) stress, and further examined how Cd amendment affected the performance and host selection of common cutworm Spodoptera litura (generalist), and alligator weed flea beetle Agasicles hygrophila (specialist). We found that the overall defense ability of invasive A. philoxeroides was higher than its native congener, but the defense mechanisms against specialist and generalist herbivores differed under Cd stress. Agasicles hygrophila was susceptible to high Cd stress, and the Cd amendment caused the beetle to shift hosts from A. philoxeroides to A. sessilis . For S. litura , organic rather than inorganic elemental defenses reduced its fitness on invasive plant, and the larvae prefer native plant against invasive plant in most scenarios. Native plant will be more vulnerable to herbivores when competing with invasive plant, especially in metal-polluted habitats. Our study provides a richer view of invasive mechanism in natural systems and appeals for paying more attention to soil contamination in assessing the potential ecological risk of plant invasion. • The overall defense of invasive A. philoxeroides is higher than native A. sessilis . • The specialist was susceptible to elemental defense. • Heavy metal promotes a host shift of specialist from invasive to native plant. • The generalist was susceptible to the organic defense. • Heavy metal promotes the plant invasion via apparent competition.

Genome-wide annotation of cuticular protein genes in non-biting midge Propsilocerus akamusi and transcriptome analysis of their response to heavy metal pollution

The insect cuticle is a sophisticated chitin-protein extracellular structure for mutable functions. The cuticles varied their structures and properties in different species, and the same species but in different regions or at different stages, to fill the requirements of different functions. The alteration of cuticle structures may also be induced due to challenges by some environmental crises, such as pollution exposures. The physical properties of the cuticle were determined by the cuticle proteins (CPs) they contain. The cuticle proteins are large protein groups in all insects, which are commonly divided into different families according to their conserved protein sequence motifs. Although Chironomidae is an abundant and universal insect in global aquatic ecosystems and a popular model for aquatic toxicology, no systematic annotation of CPs was done for any species in Chironomidae before. In this work, we annotated the CP genes of Propsilocerus akamusi, the most abundant Chironomidae species in Asia. A total of 160 CP genes were identified, and 97 of them could be well classified into eight CP families: 76 CPR genes can be subdivided into three groups (further divided into three subgroups: 36 RR1 genes, 37 RR2 genes, and 3 RR3 genes), 2 CPF genes, 3 CPLCA genes, 1 CPLCG gene, 8 CPAP genes, and 3 Tweedle genes. Additionally, we analyzed the response of P. akamusi CP genes at expression level to Cu exposure, which is related to the high heavy metal tolerance and the earlier onset of pupariation in heavy metal polluted water.

Multiscale imaging on Saxifraga paniculata provides new insights into yttrium uptake by plants

Yttrium (Y) has gained importance in high tech applications and, together with the other rare earth elements (REEs), is also considered to be an emerging environmental pollutant. The alpine plant Saxifraga paniculata was previously shown to display high metal tolerance and an intriguing REE accumulation potential. In this study, we analysed soil grown commercial and wild specimens of Saxifraga paniculata to assess Y accumulation and shed light on the uptake pathway. Laser ablation inductively coupled plasma mass spectrometry and synchrotron-based micro X-ray fluorescence spectroscopy was used to localise Y within the plant tissues and identify colocalized elements. Y was distributed similarly in commercial and wild specimens. Within the roots, Y was mostly located in the epidermis region. Translocation was low, but wild individuals accumulated significantly more Y than commercial ones. In plants of both origins, we observed consistent colocalization of Al, Fe, Y and Ce in all plant parts except for the hydathodes. This indicates a shared pathway during translocation and could explained by the formation of a stable organic complex with citrate, for example. Our study provides important insights into the uptake pathway of Y in S. paniculata, which can be generalised to other plants.

The Difference of Lead Accumulation and Transport in Different Ecotypes of Miscanthus floridulus

Miscanthus floridulus is a plant with a high biomass and heavy metal tolerance, which is a good candidate for phytoremediation. Pot experiments were conducted to compare the growth response, Pb enrichment ability, and the effect on Pb speciation of two ecotypes of M. floridulus from the Dabaoshan Mining Area and the non-mining area of Boluo County, Huizhou, in soils with different Pb contents. The results showed that two ecotypes of M. floridulus had different growth responses to Pb concentrations in soil. Under a low concentration of Pb (100 mg·kg−1) treatment, the aboveground biomass of the non-mining area plant ecotype was significantly affected, while the plants with the mining area ecotype were not significantly affected. When the concentration of Pb increased, the aboveground biomass of the non-mining ecotype was 30.2–41.1% of the control, while that of the mining ecotype was 57.8–65.0% of the control. The root biomass of the non-mining ecotype decreased with the increase of treatment concentration, accounting for 57.8–64.2% of the control, while that of the mining ecotype increased significantly, accounting for 119.5–138.6% of the control. The Pb content in the shoots and roots of the mining ecotype M. floridulus increased rapidly with the increase of the Pb treatment concentration in the soil, and the increase in speed was obviously faster than that of the non-mining ecotype. The total amount of Pb accumulated in the roots of the ecotype from the mining area was much greater than that of the ecotype from the non-mining area, and increased significantly with the increase of Pb concentration in the soil (p &lt; 0.05). With the aggravation of Pb stress, the transfer coefficient and tolerance index of the two ecotypes decreased by different degrees. The transfer coefficient and tolerance index of the mining ecotype were significantly higher than those of the non-mining ecotype. Pearson correlation analysis showed that root biomass was positively correlated with shoot biomass, and shoot biomass was negatively correlated with Pb content in both root and shoot, indicating that Pb accumulation in root and shoot was toxic to plants and inhibited the growth of M. floridulus. The mining ecotypes showed stronger tolerance to and enrichment of Pb.

Comparison of In Vitro and In Planta Heavy Metal Tolerance and Accumulation Potential of Different Armeria maritima Accessions from a Dry Coastal Meadow.

The aim of the present study was to compare the tolerance to several heavy metals and their accumulation potential of Armeria maritima subsp. elongata accessions from relatively dry sandy soil habitats in the Baltic Sea region using both in vitro cultivated shoot explants and long-term soil-cultivated plants at the flowering stage as model systems. The hypothesis that was tested was that all accessions will show a relatively high heavy metal tolerance and a reasonable metal accumulation potential, but possibly to varying degrees. Under the conditions of the tissue culture, the explants accumulated extremely high concentration of Cd and Cu, leading to growth inhibition and eventual necrosis, but the accumulation of Pb in their tissues was limited. When grown in soil, the plants from different accessions showed a very high heavy metal tolerance, as the total biomass was not negatively affected by any of the treatments. The accumulation potential for heavy metals in soil-grown plants was high, with several significant accession- and metal-related differences. In general, the heavy metal accumulation potential in roots and older leaves was similar, except for Mn, which accumulated more in older leaves. The absolute higher values of the heavy metal concentrations reached in the leaves of soil-grown A. maritima plants (500 mg Cd kg−1, 600 mg Cu kg−1, 12,000 mg Mn kg−1, 1500 mg Pb kg−1, and 15,000 mg Zn kg−1) exceeded the respective threshold values for hyperaccumulation. In conclusion, A. maritima can be characterized by a species-wide heavy metal tolerance and accumulation potential, but with a relatively high intraspecies diversity.

Fungi-derived agriculturally important nanoparticles and their application in crop stress management – Prospects and environmental risks

Nanotechnology has a wide range of agricultural applications, with emphasize on the development of novel nano-agrochemicals such as, nano-fertilizer and nano-pesticides. It has a significant impact on sustainable agriculture by increasing agricultural productivity, while reducing the use of inorganic fertilizers, pesticides, and herbicides. Nano-coating delivery methods for agrochemicals have improved agrochemical effectiveness, safety, and consistency. Biosynthesis of nanoparticles (NPs) has recently been recognized as an effective tool, contrary to chemically derived NPs, for plant abiotic and biotic stress control, and crop improvement. In this regard, fungi have tremendous scope and importance for producing biogenic NPs of various sizes, shapes, and characteristics. Fungi are potential candidates for synthesis of biogenic NPs due to their enhanced bioavailability, biological activity, and higher metal tolerance. However, their biomimetic properties and high capacity for dispersion in soil, water environments, and foods may have negative environmental consequences. Furthermore, their bioaccumulation raises significant concerns about the novel properties of nanomaterials potentially causing adverse biological effects, including toxicity. This review provides a concise outline of the growing role of fungal-mediated metal NPs synthesis, its potential applications in crop field, and associated issues of nano-pollution in soil and its future implications.

Tolerancia deAspergillus flavusyAspergillus nidulansa metales tóxicos

Introduction: Metals are found naturally in the environment, but their indiscriminate use has caused serious pollution problems. Objective: Two species of Aspergillus were isolated and identified from tailings, then their tolerance index at different concentrations of several metals was evaluated. Materials and methods: Fungi were isolated from tailings located in the Sonoran Desert. Fungal growth was evaluated in the presence of Cr6+, Pb2+, Zn2+, Ag+, Cd2+, Cu2+ and Hg2+ metals using the tolerance index and minimum inhibitory concentration (MIC). Results and discussion: A. flavus had very high tolerance indices to Cr6+, Pb2+ and Zn2+ at all concentrations evaluated (&gt;20 mM); it also had a high tolerance index to the other metals at lower concentrations. The MIC for this fungus in the presence of Cd2+, Hg2+ and Ag+ was recorded between 5 and 10 mM. The growth of A. nidulans was not inhibited with 20 mM of Cr6+. The MIC of A. nidulans in presence of Hg2+, Ag+ and Cu2+ is in the range 1-5 mM; with Cd2+, Pb2+ and Zn2+ it is in the range between 15 and 20 mM. The dose-response curves display a characteristic sigmoidal shape. With Ag+ and Cu2+A. flavus displayed a hermetic behavior. Conclusion: High metal tolerance of these fungi suggests their potential use in the removal of metals.