Different Concentrations Of Cadmium Research Articles

Study of plasma activated water effect on heavy metal bioaccumulation by Cannabis sativa Using Laser-Induced Breakdown Spectroscopy

Contamination of the environment with toxic metals such as cadmium or lead is a worldwide issue. The accumulator of metals Cannabis sativa L. has potential to be utilized in phytoremediation, which is an environmentally friendly way of soil decontamination. Novel non-thermal plasma-based technologies may be a helpful tool in this process. Plasma activated water (PAW), prepared by contact of gaseous plasma with water, contains reactive oxygen and nitrogen species, which enhance the growth of plants. In this study, C. sativa was grown in a short-term toxicity test in a medium which consisted of plasma activated water prepared by dielectric barrier discharge with liquid electrode and different concentrations of cadmium or lead. Application of PAW on heavy metal contaminated C. sativa resulted in increased growth under Pb contamination as was determined by ecotoxicology tests. Furthermore, the PAW influence on the bioaccumulation of these metals as well as the influence on the nutrient composition of plants was studied primarily by applying Laser-induced breakdown spectroscopy (LIBS). The LIBS elemental maps show that C. sativa accumulates heavy metals mainly in the roots. The results present a new proof-of-concept in which PAW could be used to improve the growth of plants in heavy metal contaminated environment, while LIBS can be implemented to study the phytoremediation efficiency.

Gill alterations of whiteleg shrimp (Litopenaeus vannamei) exposed to cadmium under different experimental salinities.

Heavy metals are one of the most important environmental pollutants in marine coastal ecosystems. Cadmium is a heavy metal that enters to marine environments via industrial wastes and oil production activities. This study were done to determine the toxicity of cadmium to Litopenaeus vannamei and to evaluate the histological changes in gill tissues after exposure to sublethal concentrations of cadmium at different salinities. For this reason, toxicity test was done to determine the lethal concentration (LC50) of cadmium for whiteleg shrimp. According to the calculated LC50 amount, sublethal doses of cadmium were used to determine its histological effects in different salinity during 2 weeks exposing period. LC50 of cadmium for 96h for whiteleg shrimp was 6.56mg/L. Histological alterations in the gill were observed in L. vannamei after 14 days exposure to different concentrations of cadmium and salinity. Histopathological index was increased in a dose-dependent manner. Our findings showed that doses lower than 2mg/L have repairable effects on gill structure, but the concentration of 2mg/L cadmium leaves irreparable and destructive effects on the gill tissue.

Phytoremediation potential of Brassica oleracea varieties through cadmium tolerance gene expression analysis

BackgroundBrassica oleracea var. acephala, commonly referred to as kale, is a well-documented plant species, a food crop but well recognized for its capacity to endure and manage the accumulation of heavy metals. In this research, the phytoremediation potential of kale was evaluated based on cadmium intake, utilizing three distinct kale varieties originating from Bosnia and Herzegovina. All kales were grown in controlled conditions, with different concentrations of cadmium (Cd), a known strong pollutant found in small concentrations in soil under normal environmental conditions. After the root length analysis and cadmium atomic spectrometry, we utilized quantitative PCR (qPCR) and cycle threshold (Ct) values to calculate the expression levels of five genes associated with Cd heavy metal response: Mitogen-activated protein kinase 2 (MAPK2), Farnesylated protein 26 and 27 (HIPP26, HIPP27), Natural resistance-associated macrophage protein 6 (RAMP6), and Heavy metal accumulator 2 (HMA2). ResultsThe atomic reader's analysis of rising cadmium concentrations revealed a proportional decline in the length of kale roots. The gene expression levels corresponded to cadmium stress differently among varieties, but mostly showing notable up-regulations under Cd stress, indicating the strong Cd presence within the plant. ConclusionsThis study demonstrated differences in gene expression behavior among three B. oleracea varieties from Bosnia and Herzegovina, indicating and filtering the Cd-resistant kale, and kale varieties suitable for phytoremediation. For the first time, such a study was conducted on kale varieties from Bosnia and Herzegovina, analyzing the impact of cadmium on the growth and resilience of these species.

Mechanism of miR-221-3p inhibiting cadmium-induced apoptosis of TM3 cells through DDIT4

To investigate the mechanism of DNA-damage-inducible transcript 4(DDIT4)targeting miR-221-3p in microRNA(miRNA) on cadmium-induced apoptosis of mouse testicular stromal cells. The activity of mouse testicular interstitial cells(TM3) was detected by CCK-8 after exposure to different concentrations of cadmium(0, 10, 20, 30, 40 μmol/L). Total RNA was extracted from cadmium-treated TM3 cells, and the significantly differentially expressed miRNA was screened with fold change(FC)>1.2 and P<0.05 as the criterion. TM3 cells were divided into blank control group, negative control group, cadmium exposure group(CdCl_2, 20 μmol/L), and cadmium+miR-221-3p mimic group. miR-221-3p mimic group was transfected into TM3 cells first, combined with cadmium exposure for 24 hours. The cell morphology was detected by Hoechst staining, and the apoptosis rate was analyzed by flow cytometry. Quantitative real-time PCR(qRT-PCR) and Western blot were used to detect DDIT4 expression. Dual luciferase reporter gene assay verified the binding of miR-221-3p to DDIT4. The function of DDIT4 and its relationship with apoptosis were analyzed by bioinformatics. The expression levels of B-cell lymphoma-2(Bcl-2) and Bcl-2 associated X protein(BAX) were observed after overexpression of miR-221-3p. Cadmium treatment of TM3 cells could reduce cell activity and there was a dose-effect relationship. The cell morphology showed that compared with the control group, the cells were wrinkled and the nuclei were heavily stained, and the apoptosis rate increased to 19.66%±0.45%(P<0.01). Compared with the cadmium exposure group, the normal morphologic cells increased in the cadmium exposure +miR-221-3p mimic group, and the apoptosis rate decreased to 13.76%±0.37%(P<0.05). The expression level of miR-221-3p was down-regulated(P<0.01), and the expression level of DDIT4 was up-regulated(P<0.05). Bioinformatics analysis and dual luciferase report analysis showed that DDIT4 was one of the target genes of miR-221-3p. Compared with the cadmium exposure group, the expression level of DDIT4 in the cadmium+miR-221-3p mimic group was down-regulated(P<0.05), and the ratio of Bcl-2/BAX was increased from 0.54±0.03 to 0.71±0.04. miR-221-3p inhibits cadmium-induced apoptosis of TM3 cells by targeting DDIT4.

Migration Behaviour of the Combined Pollutants of Cadmium and 2,2′,4,4′,5,5′-Hexabrominated Diphenyl Ether (BDE-153) in Amaranthus mangostanus L. and Their Toxicity to A. mangostanus

The effects of different concentrations of cadmium and 2,2′,4,4′,5,5′-hexabrominated diphenyl ether (BDE-153) on the growth and related physiological and biochemical indexes of Amaranthus mangostanus L. (amaranth) were studied. The results showed that the presence of BDE-153 promoted the absorption of Cd by the amaranth and inhibited the migration of Cd from the roots to the shoots. At the same time, 0.1 mg/L of Cd had a synergistic effect on the migration of BDE-153, but 5 mg/L Cd inhibited the accumulation of BDE-153 in the aboveground part of the amaranth. In addition, the kinetics of the uptake of pollutants by the amaranth showed that both Cd and BDE-153 could be transported by amaranth, but Cd and BDE-153 were mainly enriched in the roots, and the presence of Cd may cause a lag in the uptake of BDE-153 in the shoots. Compared with the control group, the biomass of the amaranth affected by BDE-153 and a high concentration of Cd (5 mg/L) decreased by 30.2–49.5%, the chlorophyll content decreased by 43.0–60.3%, the Evans blue increased, and the MDA content was higher. The activities of superoxide dismutase (SOD) and catalase (CAT) also decreased with an increase in the BDE-153 concentration. This indicates that the interaction between BDE-153 and a high concentration of Cd (5 mg/L) is more toxic to amaranth than single Cd pollution. This paper provides the necessary data support for phytoremediation of heavy metal and organic compound pollution.

Development of Conducting Biopolymer-Based Biosensor for Heavy-Metal Ion Detection

The increasing concentration of heavy metals in the water ecosystems has been a noteworthy concern nowadays. This has accounted for various diseases, due to the bioaccumulation in the human body. We propose a biocompatible, non-toxic technique for the identification of heavy metal ions from the contaminated aquatic samples. A urease biosensor, having interpenetrating network of Katira-cl-Acrylic Acid (AAc)/Polyaniline (PANI) hydrogel composite deposited onto the indium tin oxide (ITO). Enhanced hydrogel conductivity due to the incorporation of PANI has been gained by the interfacial polymerization of katira gum and aniline monomer in the ratio of 2:1 using N,N′-MBA and APS as cross-linker and initiator respectively. Structural, morphological and electrochemical characterization of PANI/ITO, Katira-cl-AAc/PANI/ITO and Urease/Katira-cl-AAc/PANI/ITO electrode conducted using SEM, FT-IR, TGA, UV spectrometry, cyclic voltammetry. A comparative study of different concentrations of cadmium, cobalt and Mercury, has been done. The inhibition rates were found to be in the order of Hg2+ > Cd2+ > Co2+. Enzyme inhibition observed in the concentration range from 1.8 mM to 5 mM, 0.1 mM to 2 mM and 0.1 mM to 5 mM respectively. Urease/Katira-cl-AAc/PANI/ITO, exhibits greater stability, enhanced sensitivity and wide-range of detection limit (200 to 270 ng l−1) with a shelf life.

Investigating the growth characteristics, oxidative stress, and metal absorption of chickpea (Cicer arietinum L.) under cadmium stress and in silico features of HMAs proteins

Heavy metal contamination can have a strong effect on the morphological and physiological characteristics of plants. In the present study, Cicer arietinum L. (chickpea) was exposed to different concentrations of cadmium (control, 2, 4, 8 μg Cd g-1 perlite) and the effect on plant growth and antioxidant enzymes were evaluated. The observed morphological changes in chickpea plant included stunted growth, reduced root system development and plant color change. A significant increase in enzyme activity of peroxidase, superoxide dismutase, catalase, and ascorbate peroxidase was observed at 4 μg Cd g-1 perlite, with a subsequent decrease when concentration was increased to 8 μg Cd g-1 perlite in the leaves of the plants. The highest cadmium levels were determined at a concentration of 8 μg Cd g-1 perlite. With the addition of 2 μg Cd g-1 perlite, manganese uptake in the aboveground part of the plant increased significantly, but then decrease at higher cadmium concentrations. In addition, zinc and copper levels decrease in the presence of cadmium. These results indicate that chickpea has a relatively high adsorption capacity for cadmium in aboveground tissues and special precautions should be taken when growing chickpea. In silico analysis led to the identification of 13 heavy metal ATPases (HMAs) in chickpea. These proteins contain 130 to 1032 amino acids with 3 to 18 exons. They are involved in the transfer of cadmium and zinc and help in heavy metal detoxification of plants. Bioinformatics studies have been conducted to better understand the mechanism by which the plant is able to combat heavy metal stress.

Tissue distribution of cadmium and its effect on reproduction in Spodoptera exigua

Vegetable fields are often contaminated by heavy metals, and Spodoptera exigua is a major vegetable pest which is stressed by heavy metals mainly by feeding. In this study, cadmium accumulation in the tissues of S. exigua exposed to cadmium and its effects on the growth and development of the parents and the offspring were investigated. Under the stress of different concentrations of cadmium (0.2, 3.2, and 51.2 mg kg–1), the cadmium content in each tissue of S. exigua increased in a dose-dependent manner. At the larval stage, the highest cadmium accumulation was found in midgut in all three cadmium treatments, but at the adult stage, the highest cadmium content was found in fat body. In addition, the cadmium content in ovaries was much higher than in testes. When F1S. exigua was stressed by cadmium and the F2 generation was not fed a cadmium-containing diet, the larval survival, pupation rate, emergence rate and fecundity of the F2 generation were significantly reduced in the 51.2 mg kg–1 treatment compared to the corresponding F1 generation. Even in the F2 generation of the 3.2 mg kg–1 treatment, the fecundity was significantly lower than in the parental generation. The fecundity of the only-female stressed treatment was significantly lower than that of the only-male stressed treatment at the 3.2 and 51.2 mg kg–1 cadmium exposure levels. When only mothers were stressed at the larval stage, the fecundity of the F2 generation was significantly lower than that of the F1 generation in the 51.2 mg kg–1 treatment, and it was also significantly lower than in the 3.2 and 0.2 mg kg–1 treatments. The results of our study can provide useful information for forecasting the population increase trends under different heavy metal stress conditions and for the reliable environmental risk assessment of heavy metal pollution.

Responses of rhizosphere microbial community structure and metabolic function to heavy metal coinhibition.

Metal mineral mining results in releases of large amounts of heavy metals into the environment, and it is necessary to better understand the response of rhizosphere microbial communities to simultaneous stress from multiple heavy metals (HMs), which directly impacts plant growth and human health. In this study, by adding different concentrations of cadmium (Cd) to a soil with high background concentrations of vanadium (V) and chromium (Cr), the growth of maize during the jointing stage was explored under limiting conditions. High-throughput sequencing was used to explore the response and survival strategies of rhizosphere soil microbial communities to complex HM stress. The results showed that complex HMs inhibited the growth of maize at the jointing stage, and the diversity and abundance of maize rhizosphere soil microorganisms were significantly different at different metal enrichment levels. In addition, according to the different stress levels, the maize rhizosphere attracted many tolerant colonizing bacteria, and cooccurrence network analysis showed that these bacteria interacted very closely. The effects of residual heavy metals on beneficial microorganisms (such as Xanthomonas, Sphingomonas, and lysozyme) were significantly stronger than those of bioavailable metals and soil physical and chemical properties. PICRUSt analysis revealed that the different forms of V and Cd had significantly greater effects on microbial metabolic pathways than all forms of Cr. Cr mainly affected the two major metabolic pathways: microbial cell growth and division and environmental information transmission. In addition, significant differences in rhizosphere microbial metabolism under different concentrations were found, and this can serve as a reference for subsequent metagenomic analysis. This study is helpful for exploring the threshold for the growth of crops in toxic HM soils in mining areas and achieving further biological remediation.

Egg white composition, antioxidant capacity, serum and yolk lipids and oxidative damage of the oviduct magnum in laying hens fed diets contaminated with different concentrations of cadmium

Total of 384 healthy 38-week-old hens were randomly divided into four treatments. Layers in four groups were fed a basal diet and a basal diet with Cd at the level of 15, 30 and 60 mg/kg for nine weeks. Results showed that Cd could dose-dependently deposited in magnum and a positive correlation occurred between the accumulation of Cd in magnum and Cd content in egg whites. When compared with control group, 60 mg/kg Cd decreased magnum ovomucin, ovalbumin, lysozyme and ovomucoid gene expressions, but increased avidin gene expression obviously. Hens receiving 60 mg/kg Cd exhibited a significant decrease in egg white ovalbumin content and its proportion in total protein and increase in total cholesterol and LDLC levels in serum and yolk. The level of GSH and activities of T-SOD and CAT in magnum and GSH-Px activity in egg white were decreased significantly, while MDA level in both magnum and egg white was increased obviously in 60 mg/kg Cd group. Besides, Cd induced oxidative stress, inflammation, endoplasmic reticulum stress (ERS) and mitophagy accompanied by a significant up-regulation of the expressions of Keap1, IL1β, TNFα, NF-κB, p65, p-p65, Grp78, CHOP, ATF4, ATF6, IRE1α, Grp94, PINK1, Parkin, Fundc1, GRP75, VDAC1, MCU, MFF, Bnip3 and LC3I/II and a significant down-regulation of the expressions of Nrf2, HO-1, SOD1, SOD2, SOD3, MFN1, MFN2 and PGC1α. These results indicated that Cd can increase serum and yolk cholesterol level and induce magnum oxidative stress, inflammation, ERS and mitophagy through Nrf2/NF-κB and IRE1α/IP3R/GRP75/VDAC1/MCU pathways, thus disrupting egg white composition. Highlights Cd exposure disrupted the synthesis of egg white protein in oviduct magnum and destroyed antioxidant status and protein composition in egg white. Cd exposure significant enhanced serum and yolk total cholesterol and LDL cholesterol levels. Cd exposure induced magnum oxidative stress, inflammation, ERS and mitophagy through Nrf2/NF-κB and IRE1α/IP3R/GRP75/VDAC1/MCU pathways.

Tolerance of Vallisneria sp. for Different Concentrations of Cadmium and Lead

This study was done to recognize the tolerance of Vallisneria sp. for different concentrations of cadmium and lead in aqueous ecosystem. The concentrations of 30, 40, 50 mg/L were used for Cd and Pb in three replications for each concentration for 30 days. 
 The results found that the plant was tolerated 50 mg/L of Pb, and 40 mg/L of Cd. Significant differences were found in removing capacity by plant for Cd and Pb, in all concentrations 30, 40, 50 mg/L during experiment period. There were no morphological changes in the first day of the experiment period, but it was appeared after the threeth days of the experiment, and it continued till the end of the experiment. 
 The highest removal ratio for Pb was 97.66% in the concentration 30 mg/L, and the lowest removal ratio was 57.4% in the concentration 50 mg/L. For Cd the highest removal ratio 80.06% in concentrations 30 mg/L and the lowest removal ratio was 76.2% mg/L in concentrations 50 mg/L.

Identification of a Green Algal Strain Collected from the Sarno River Mouth (Gulf of Naples, Italy) and Its Exploitation for Heavy Metal Remediation.

Heavy metals (HMs) can induce both chronic and acute harmful effects on marine and freshwater biota. The environmental impact of HMs in freshwater, seawater, soil, and wastewater can be limited using microbes, including microalgae, that are able to remove metals from environmental matrices. Indeed, they can passively adsorb and actively accumulate these persistent pollutants within their organelles, limiting their detrimental effects on cellular metabolism. The Sarno River is a 30 km long freshwater stream located in Southern Italy, polluted by partially untreated municipal, agricultural, and industrial wastewaters. In spite of this, microalgal cultures from Sarno River or Sarno River Mouth have never been established. In the present study, we isolated a green algal strain from the Sarno River Mouth and determined its ability to grow in polluted seawater containing different concentrations of cadmium, lead, or zinc. This strain was found to be able to accumulate these elements within its biomass in a dose-dependent manner. Growth inhibition experiments confirm the relatively low toxicity of Cd and Pb below 50 µM, while algal growth was seriously affected in Zn-amended media. To the best of our knowledge, this is the first study focused on the ability of microalgae from Sarno River Mouth to tolerate and uptake HMs.

Enhanced photocatalytic efficiency of TiO2/CdS nanocomposites by manipulating CdS suspension on TiO2 nanoparticles

• TiO 2 /CdS nanocomposites are synthesized at different concentrations of cadmium and sulphur precursors. • The Cd and S precursors ratios affect the size and morphologies of resulting nanocomposites. • Photocatalytic activities are influenced by the precursor ratio. • Stepwise de-ethylation for RhB is observed during visible light photocatalysis. Titanium Dioxide (TiO 2 ) has long been found to be a promising photocatalyst in the ultraviolet region, although it faces several limitations in the visible range. Various attempts for overcoming these shortcomings have shown that TiO 2 nanocomposites offer excellent results for visible area photocatalysis. In the present work, three different samples of TiO 2 /CdS nanocomposites are synthesized using simple and cost-effective hydrothermal method, based on different concentrations of cadmium and sulphur precursors and a comparison is made among them. Characterization techniques like Scanning Electron Microscopy (SEM), Photoluminescence (PL) spectroscopy, UV-visible spectroscopy, X-Ray Diffraction (XRD), Energy Dispersive X-Ray Analysis (EDX) and Fourier Transform Infrared (FTIR) spectroscopy are employed to study morphological, optical, structural, and elemental properties of the as-synthesized nanocomposites. SEM analysis shows that change in concentration of precursors caused morphological changes in the resulting samples. XRD characterization shows that the crystallite size gets modified at different concentrations ranging from approximately 21 nm to 5 nm. As per the UV-Vis spectroscopy, the band gap of TiO 2 /CdS nanocomposites has substantially decreased, making it highly suitable for photocatalytic application in the visible region in comparison to pure TiO 2 . Photocatalytic degradation processes for as-synthesized TiO 2 /CdS nanocomposites are studied for methylene blue (MB) and rhodamine B (RhB) dyes under visible light exposure. Results demonstrate that degradation results for MB dye are better in comparison to RhB dye for all the three synthesized photocatalysts. Futher, it is concluded that TiO 2 /CdS nanocomposite with a 1:1 molar ratio of cadmium and sulphur precursors has the optimum photocatalytic performance for dye degradation.

Increasing the resistance of barley sprouts by priming with heavy metal salts

The article investigated the different concentrations of cadmium and lead salts influence to the growth and development of barley plant shoots. As a response of sprouts to the action of lead and cadmium ions, changes in the accumulation of their wet and dry biomass, the height of the sprouts, as well as survival were evaluated. Since CdCl2 and Pb(CH3COO)2 belong to the group of heavy metals with a strong toxic effect, when they are individually administered, there is a decrease in the growth of shoots and a slowdown in development due to the accumulation of wet and dry biomass of the plant. While inhibition of sprouts at a concentration of Pb(CH3COO)2 0.5-10 mM reduced sprouts by 2-10 times, the effect of CdCl2 on barley sprouts in high concentrations led to a halt in the accumulation of dry mass. Processing of barley sprouts before sowing with a low concentration of lead and cadmium salts increases their resistance to metals and allows in the future to transport the effects of high concentrations of these substances without damage and with minimal inhibition of growth processes. In addition, these metals are powerful inducers of phytochelatin synthesis. Thus, the accumulation of osmoprotectants is unlikely to play an important role in cell detoxification from heavy metals. Apparently, the possible role of the accumulation of osmoprotectants in the presence of heavy metals is not necessarily associated with metal chelation. First, heavy metals usually disrupt the water balance in the cell. It is known that water deficiency always leads to the accumulation of osmoprotectants in the plant cell. The accumulation function of osmoprotectants caused by heavy metals may be more associated with osmoregulation and enzyme protection against dehydration than with direct metal chelation. Keywords: the growth and development of barley sprouts, lead and cadmium salts, priming, stability.

E2Fs co-participate in cadmium stress response through activation of MSHs during the cell cycle.

Cadmium is one of the most common heavy metal contaminants found in agricultural fields. MutSα, MutSβ, and MutSγ are three different MutS-associated protein heterodimer complexes consisting of MSH2/MSH6, MSH2/MSH3, and MSH2/MSH7, respectively. These complexes have different mismatch recognition properties and abilities to support MMR. However, changes in mismatch repair genes (OsMSH2, OsMSH3, OsMSH6, and OsMSH7) of the MutS system in rice, one of the most important food crops, under cadmium stress and their association with E2Fs, the key transcription factors affecting cell cycles, are poorly evaluated. In this study, we systematically categorized six rice E2Fs and confirmed that OsMSHs were the downstream target genes of E2F using dual-luciferase reporter assays. In addition, we constructed four msh mutant rice varieties (msh2, msh3, msh6, and msh7) using the CRISPR-Cas9 technology, exposed these mutant rice seedlings to different concentrations of cadmium (0, 2, and 4 mg/L) and observed changes in their phenotype and transcriptomic profiles using RNA-Seq and qRT-PCR. We found that the difference in plant height before and after cadmium stress was more significant in mutant rice seedlings than in wild-type rice seedlings. Transcriptomic profiling and qRT-PCR quantification showed that cadmium stress specifically mobilized cell cycle-related genes ATR, CDKB2;1, MAD2, CycD5;2, CDKA;1, and OsRBR1. Furthermore, we expressed OsE2Fs in yeasts and found that heterologous E2F expression in yeast strains regulated cadmium tolerance by regulating MSHs expression. Further exploration of the underlying mechanisms revealed that cadmium stress may activate the CDKA/CYCD complex, which phosphorylates RBR proteins to release E2F, to regulate downstream MSHs expression and subsequent DNA damage repairment, thereby enhancing the response to cadmium stress.

Time-Dependent Toxicity and Health Effects Mechanism of Cadmium to Three Green Algae.

As algae are extremely sensitive to heavy-metal ions and can be critical biological indicators in the heavy-metal toxicity analyses conducted by environmental health researchers, this paper explores the sensitivity to temporal toxicity of three species of green algae: Scenedesmus obliquus, Chlorella pyrenoidosa, and Selenastrum capricornutum. The method of time-dependent microplate toxicity analysis was used to systematically investigate the changes in the toxicities of the three green-algae species induced by different concentrations of cadmium (Cd). The chlorophyll a content, antioxidant enzyme activity, and malondialdehyde (MDA) content in the algae were analyzed to explore the mechanism of Cd toxicity after 96 h of exposure. The results showed that the toxic effects of Cd on the three algae species were time-dependent. By comparing the toxic effect of Cd, indicated by pEC50 (the negative logarithm of EC50), on the algae species at four durations of exposure (24, 48, 72, and 96 h), this study found that the indicator organisms had different sensitivities to Cd. The order of sensitivity was C. pyrenoidosa > S. obliquus > S. capricornutum. Cd exposure had significant effects on the chlorophyll a and MDA content and on the enzyme activity of superoxide dismutase (SOD) and catalase (CAT) in the algae species. The chlorophyll a content in the cells of the algae decreased with increasing Cd concentration. The enzyme activity of CAT and content of MDA increased with increasing Cd concentration, which indicated that Cd had an oxidative stress effect on the three algae species.

Comparison of the combined toxicity of polystyrene microplastics and different concentrations of cadmium in zebrafish

Microplastic particles (MPs) are widely distributed in the environment. The high surface ratio of MPs make them effective transmission mediums for many toxic pollutants. The combined toxicity of MPs and heavy metals have received increasing attention in recent years. In this study, effects of MPs (100 μg/L) on the toxicity of low (15 μg/L) and high (150 μg/L) concentrations of cadmium (Cd) to zebrafish were evaluated based on a 10-day subacute exposure. The survival rate, growth, antioxidant capacity, reactive oxygen species (ROS) accumulation, histology and Cd biological enrichment in different tissues were investigated with the objective to understand the effect and mechanism of MPs on Cd toxicity to zebrafish. The results showed that the effect of MPs on Cd toxicity mainly depended on the concentration of Cd. MPs significantly enhanced the toxicity of low concentrations of Cd (LCd), including lower antioxidant enzyme activities, higher ROS levels, more severe tissue damage, inhibited growth rate and lower survival rate. However, the effects of MPs on the toxicity of high concentrations of Cd (HCd) were exactly opposite to LCd. Cd enrichment analysis showed that MPs could significantly increase LCd accumulation in intestine, gill, skin and muscle tissues, while decrease the enrichment of HCd in liver, intestine, gill and muscle tissues. Free Cd in the exposure water was significantly decreased by MPs in the HCd and MPs combined exposure group. These results suggest that effect of MPs on Cd toxicity to zebrafish depending on Cd concentration, MPs can increase the enrichment of LCd in zebrafish and enhance its toxicity, but can decrease the enrichment of HCd in zebrafish and attenuate its toxicity. The present study will broaden our understanding of the interaction between MPs and heavy metals.

Intraspecific variability in herbivore response to elemental defences is caused by the metal itself

Some plants are able to accumulate on their leaves metals taken from the soil, using this as a defence against herbivorous arthropods. However, herbivore response to metal accumulation in plants is known to be variable. While some species and taxonomic groups are less affected than others, hormetic effects have also been observed in spider mites, herbivorous crop pests. Still, knowledge on the range and causes of intraspecific variation in the response of herbivores to metal accumulation is lacking. Here, using two species of spider mites, Tetranychus urticae and Tetranychus evansi, we tested the variation in 17 populations in response to cadmium-accumulating tomato plants and the drivers of such variation. We observed a nonlinear, hormetic response of mites to plants with cadmium in some, but not all, populations. The same pattern was recaptured in artificial diets with different concentrations of cadmium but not in artificial diets with sugars, which change in the plant in response to cadmium. This indicates that herbivores on metal-accumulating plants respond to metals, not to the variations in leaf carbohydrates. Therefore, metals exert different effects on herbivores according to the amount accumulated, but independently of other studied plant traits. This knowledge is key to the understanding of the mechanisms underlying herbivore responses to metal-based plant defences and to pesticides containing heavy metals. Additionally, our findings draw attention to the need of considering intraspecific variation and nonlinearities when studying the effects of metals and other contaminants on herbivorous arthropods.

Alleviation of cadmium stress in rice by inoculation of Bacillus cereus.

Heavy metal resistant bacteria are of great importance because they play a crucial role in bioremediation. In the present study, 11 bacterial strains isolated from industrial waste were screened under different concentrations of cadmium (Cd) (100 µM and 200 µM). Among 11 strains, the Cd tolerant Bacillus cereus (S6D1–105) strain was selected for in vitro and in vivo studies. B. cereus was able to solubilize potassium, and phosphate as well as produce protease and siderophores during plate essays. Moreover, we observed the response of hydroponically grown rice plants, inoculated with B. cereus which was able to promote plant growth, by increasing plant biomass, chlorophyll contents, relative water content, different antioxidant enzymatic activity such as catalase, superoxide dismutase, ascorbate peroxidase, polyphenol oxidase and phenylalanine ammonia-lyase and reducing malondialdehyde content in both roots and leaves of rice plants under Cd stress. Our results showed that the B. cereus can be used as a biofertilizer which might be beneficial for rice cultivation in Cd contaminated soils.

Comparison of Growth Performance, Pigment Synthesis, and Esterase Activity of Synechococcus sp. HS01 and Limnothrix sp. KO01 in Response to Cadmium Toxicity.

Various studies have been conducted to understand the impact of environmental pollutants on cyanobacteria due to their abundant presence in aquatic and terrestrial environments, specific morphological and physiological characteristics, and high ecological flexibility in response to environmental changes. Here, the effect of different concentrations of cadmium on two native strains of cyanobacteria, namely Synechococcus sp. HS01 and Limnothrix sp. KO01 was studied and compared with each other. In this regard, the cyanobacterial growth, pigment contents, and esterase enzyme activity were evaluated after exposure of the cells to different concentrations of cadmium (II). The toxic effects of Cd(II) on the growth rate of Limnothrix sp. KO01, even at low concentrations, tended to be higher than those for Synechococcus sp. HS01. The content of pigments decreased by an increase in Cd(II) concentration. In compliance with the cell growth, the changes occurred in pigment contents of Limnothrix sp. KO01 was more sensitive than Synechococcus sp. HS01 in the presence of different concentrations of cadmium. Flow cytometry analysis of Cd(II) effects on esterase activity of both strains after 6, 24, 48, and 72h of exposure to Cd(II) concentrations of 9, 27, 63, and 90μM showed that tolerance to Cd(II) toxicity in Limnothrix sp. KO01 is less than Synechococcus sp. HS01. The results obtained in this study suggest high potentials of Synechococcus sp. HS01 for heavy metal bioaccumulation due to its considerable tolerance to cadmium.