The effect of different amendments on Cd availability and bacterial community after three-year consecutive application in Cd-contaminated paddy soils.

In situ immobilization is a widely used measure for passivating Cd-contaminated soils. Amendments need to be continuously applied to achieve stable remediation effects. However, few studies have evaluated the impact of consecutive application of amendments on soil health and the microecological environment. A field experiment was conducted in a Cd-contaminated paddy (available Cd concentration 0.40 mg kg-1) on the Chengdu Plain to investigate the changes in soil Cd availability and response characteristics of soil bacterial communities after consecutive application of rice straw biochar (SW), fly ash (FM) and marble powder (YH) amendments from 2018 to 2020. Compared with control treatment without amendments (CK), soil pH increased by 0.6, 0.5 and 1.5 under SW, FM and YH amendments, respectively, and the soil available Cd concentration decreased by 10.71%, 21.42% and 25.00%, respectively. The Cd concentration in rice grain was less than 0.2 mg kg-1 under YH amendment, which was within the Chinese Contaminant Limit in Food of National Food Safety Standards (GB2762-2022) in the second and third years. The three amendments had different effects on the transformation of Cd fractions in soil, which may be relevant to the specific bacterial communities shaped under different treatments. The proportion of Fe-Mn oxide-bound fraction Cd (OX-Cd) increased by 11% under YH treatment, which may be due to the promotion of Fe(III) and Cd binding by some enriched iron-oxidizing bacteria, such as Lysobacter, uncultured_Pelobacter sp. and Sulfurifusis. Candidatus_Tenderia and Sideroxydans were enriched under SW and FM amendments, respectively, and were likely beneficial for reducing Cd availability in soil through Cd immobilization. These results revealed the significance of the bacterial community in soil Cd immobilization after consecutive application of amendments and highlighted the potential of applying YH amendment to ensure the safe production of rice in Cd-contaminated soil.

Association between exposure to heavy metals in atmospheric particulate matter and sleep quality: A nationwide data linkage study.

BACKGROUND: Recent studies have demonstrated that long-term exposure to particulate matter (PM) is associated with poor sleep quality. However, no studies have linked PM constituents, particularly heavy metals, to sleep quality. OBJECTIVE: This study investigated the association between exposure to heavy metals in PM and sleep quality. METHODS: We obtained nationwide data from the Korean Community Health Survey conducted in 2018 among adults aged 19-80 years. Sleep quality was evaluated using Pittsburgh Sleep Quality Index (PSQI). Poor sleep quality was defined as PSQI ≥5. One-year and three-month average concentrations of heavy metals (lead, manganese, cadmium, and aluminum) in PM with diameter ≤10 µm were obtained from nationwide air quality monitoring data and linked to the survey data based on individual district-level residential addresses. Logistic regression analyses were performed after adjusting for age, gender, education level, marital status, smoking status, alcohol consumption, history of hypertension, and history of diabetes mellitus. RESULTS: Of 32,050 participants, 17,082 (53.3%) reported poor sleep quality. Increases in log-transformed one-year average lead (odds ratio, 1.14; 95% confidence interval, 1.08-1.20), manganese (1.31; 1.25-1.37), cadmium (1.03; 1.00-1.05), and aluminum concentrations (1.17; 1.10-1.25) were associated with poor sleep quality. Increases in log-transformed three-month average manganese (odds ratio, 1.13; 95% confidence interval, 1.09-1.17) and aluminum concentrations (1.28; 1.21-1.35) were associated with poor sleep quality. CONCLUSION: We showed for the first time that exposure to airborne lead, manganese, cadmium, and aluminum were associated with poor sleep quality. This study may be limited by self-reported sleep quality and district-level exposure data.

Selenium and zinc alleviate hepatotoxicity induced by heavy metal mixture (cadmium, mercury, lead and arsenic) via attenuation of inflammo-oxidant pathways.

Heavy metals (HM) are believed to be injurious to humans. Man is exposed to them on daily basis unknowingly, with no acceptable protocol to manage its deleterious effects. These metals occur as mixture of chemicals with varying concentrations in our atmosphere. There are growing calls for the use of essential metals in mitigating the injurious effects induced by heavy metals exposure to man; therefore, the aim of this study was to evaluate the protective effects of essential metals (Zinc and Selenium) in a mixture of heavy metal toxicity. In this study, except for negative controls, all other groups were treated with lead (PbCl2 , 20 mg kg-1 ); cadmium (CdCl2 , 1.61 mg kg-1 ); mercury (HgCl2 , 0.40 mg kg-1 ), and arsenic (NaAsO3, 10 mg kg-1 ) that were formed in distilled water. Pb, Cd, As, and Hg were administered as mixtures to 35, 6 weeks old rats weighing between 80 to 100 g for 60 days. Group I served as normal control without treatment, group II positive control received HM mixture, while groups III to V received HMM with Zn, Se, and Zn + Se respectively. Animal and liver weights, HM accumulation in the liver, food intake (FI), water intake (WI), liver function test, malondialdehyde (MDA), and inflammatory/transcription factor/apoptosis markers were checked. Also, antioxidant enzymes, and histological studies were carried out. Metal mixture accumulated in the liver and caused toxicities which were ameliorated by Zn and Se administration. HM caused significant decrease in FI, WI and distorted the level of liver enzymes, lipid peroxidation, inflammatory markers, antioxidants and architecture of the liver. Co administration with Zn or Se or both reversed the distortions. This study lays credence to the evolving research on the public health implications of low dose metal mixtures and the possible ameliorative properties of Zn and Se.

Modeling spatial trends and exchange fluxes of contaminants in agricultural soil under pollution prevention measures.

Modeling the long-term trends of contaminants in topsoil under controlled measures is critical for sustainable agricultural environmental management. Traditional mass balance equations cannot predict spatial variation and exchange flux of regional soil contaminants for it lacks a method of assigning input-output parameters to each simulated cell. To overcome this limitation, we allocate the estimated source contribution flux to the spatial grid cell in the regional chemical mass balance by integrated positive matrix factorization (P-RCMB) with historical trends quantification. Focusing on Cd and As, which are elements with elevated risks of food intake and volatilization/infiltration, the model is applied to 30 ha of agricultural land near the enterprise. Predictions indicate an additional 13.5% of the soil is contaminated, and approximately 2.57 ha may accrue after 100 years at the site, with an uncertainty range of 0.98-5.3 ha. Clean water irrigation (CWI) reduces contamination expansion by approximately 42%, including approximately 4813 g ha-1 yr-1 net As infiltration, playing a dominant role in preventing the formation of severely contaminated soil. Stop straw return, green fertilizers use, and reduced atmospheric deposition control the exchange flux of Cd (114.9 g ha-1 yr-1) in moderate/slight contamination areas. For the different contaminants' cumulative trends in dryland and paddy fields, achieving a net cumulative flux close to zero in marginally contaminated areas presents a viable approach to optimize current emission standards. if trade-off straw removal and additional fertilizer inputs, a straw return rate of approximately 40% in Cd-contaminated soil will yield overall benefits. This model contributes valuable insights and tools for policymaking in contaminated land sustainable utilization and emission standard optimization.

Air, land, and water pollutants and public health expenditures: Empirical data from selected EU countries in the transport sector.

The increase in economic activity, particularly in transport, leads to a significant increase in emissions of pollutants, such as ammonia, arsenic and cadmium, at the European Union (EU) level. This can seriously impact human health and, consequently, public health spending. Based on data from 15 European Union countries from 1992 to 2020, a panel co-integration approach is used to study these pollutants' short- and long-term co-movements and per capita health expenditure. The results show a long-term relationship between ammonia, arsenic and cadmium emissions and per capita health spending, as they are panel-cointegrated. Ammonia and cadmium emissions exert a statistically significant positive effect on health expenditure in the short run, and arsenic emissions have a statistically significant positive impact in the long run. The forecast assessment of reductions in health spending resulting from policies to reduce emissions of air, land and water pollutants, such as ammonia, arsenic and cadmium, from the transport sector supports investments in its policies that reduce pressure on health spending. The reduction in annual healthcare expenditure is greater when these reductions are made sooner and more severely. Indeed, varying the reduction in emissions for each pollutant by 10% and 100%, respectively, from the first year for all countries over a 3-year period results in an average annual reduction in health spending of 2.05% and 51.02%, respectively. However, if we wait until the third year, the annual reduction is only 0.77% and 17.63% respectively.

Adsorption behavior of lead, cadmium, and arsenic on manganese-modified biochar: competition and promotion.

Biochar adsorption of heavy metals has been a research hotspot, yet there has been limited reports on the effect of heavy metal interactions on adsorption efficiency in complex systems. In this study, the adsorbent was prepared by pyrolysis of rice straw loaded with manganese (BC-Mn). The interactions of Pb, Cd and As adsorption on BC-Mn were systematically studied. The results of the adsorption isotherms for the binary metal system revealed a competitive adsorption between Pb and Cd, resulting in decreased Pb (from 214.38 mg/g to 148.20 mg/g) and Cd (from 165.73 mg/g to 92.11 mg/g). A notable promotion occurred between As and Cd, showing an increase from 234.93 mg/g to 305.00 mg/g for As and 165.73 mg/g to 313.94 mg/g for Cd. In the ternary metal system, Pb inhibition did not counteract the promotion of Cd and As. Furthermore, the Langmuir isotherm effectively described BC-Mn's adsorption process in monometallic, binary, and ternary metal systems (R2 > 0.9294). Zeta and FTIR analyses revealed simultaneous competition between Pb and Cd for adsorption on BC-Mn's -OH sites. XPS analysis revealed that As adsorption by BC-Mn facilitated the conversion of MnO2 and MnO to MnOOH, resulting in increased hydroxyl radical production on BC-Mn's surface. Simultaneously, Cd combined with the adsorbed As to form ternary Cd-As-Mn complexes, which expedited the removal of Cd. These results help to provide theoretical support as well as technical support for the treatment of Pb-Cd-As contaminated wastewater.

Polyamine-producing bacteria inhibit the absorption of Cd by spinach and alter the bacterial community composition of rhizosphere soil.

Polyamines (PAs) are small aliphatic nitrogenous bases with strong biological activity that participate in plant stress response signaling and the alleviation of damage from stress. Herein, the effects of the PA-producing bacterium Bacillus megaterium N3 and PAs on the immobilization of Cd and inhibition of Cd absorption by spinach and the underlying mechanisms were studied. A solution test showed that strain N3 secreted spermine and spermidine in the presence of Cd. Both strain N3 and the PAs (spermine+spermidine) immobilized Cd and increased the pH of the solution. Untargeted metabolomics results showed that strain N3 secreted PAs, N1-acetylspermidine, 3-indolepropionic acid, indole-3-acetaldehyde, cysteinyl-gamma-glutamate, and choline, which correlated with plant growth promotion and Cd immobilization. A pot experiment showed that rhizosphere soil inoculation with strain N3 and PAs improved spinach dry weight and reduced spinach Cd absorption compared with the control. These positive effects were likely due to the increase in rhizosphere soil pH and NH4+-N and PA contents, which can be attributed primarily to Cd immobilization. Moreover, inoculation with strain N3 more effectively inhibited the absorption of Cd by spinach than spraying PAs, mainly because strain N3 enabled a better relative abundance of bacteria (Microvirga, Pedobacter, Bacillus, Brevundimonas, Pseudomonas, Serratia, Devosid, and Aminobacter), that have been reported to have the ability to resist heavy metals and produce PAs. Strain N3 regulated the structure of rhizosphere functional bacterial communities and inhibited Cd uptake by spinach. These results provide a theoretical basis for the prevention of heavy metal absorption by vegetables using PA-producing bacteria.

Integrated physiological and omics analyses reveal the mechanism of beneficial fungal Trichoderma sp. alleviating cadmium toxicity in tobacco (Nicotiana tabacum L.).

Cadmium (Cd) is a highly toxic heavy metal and readily accumulates in tobacco, which imperils public health via Cd exposure from smoking. Beneficial microbes have a pivotal role in promoting plant growth, especially under environmental stresses such as heavy metal stresses. In this study, we introduced a novel fungal strain Trichoderma nigricans T32781, and investigated its capacity to alleviate Cd-induced stress in tobacco plants through comprehensive physiological and omics analyses. Our findings revealed that T32781 inoculation in soil leads to a substantial reduction in Cd-induced growth inhibition. This was evidenced by increased plant height, enhanced biomass accumulation, and improved photosynthesis, as indicated by higher values of key photosynthetic parameters, including the maximum quantum yield of photosystem Ⅱ (Fv/Fm), stomatal conductance (Gs), photosynthetic rate (Pn) and transpiration rate (Tr). Furthermore, element analysis demonstrated that T. nigricans T32781 inoculation resulted in a remarkable reduction of Cd uptake by 62.2% and a 37.8% decrease in available soil Cd compared to Cd-stressed plants without inoculation. The protective role of T32781 extended to mitigating Cd-induced oxidative stress by improving antioxidant enzyme activities of superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX). Metabolic profiling of tobacco roots identified 43 key metabolites, with notable contributions from compounds like nicotinic acid, succinic acid, and fumaric acid in reducing Cd toxicity in T32781-inoculated plants. Additionally, rhizosphere microbiome analysis highlighted the promotion of beneficial microbes, including Gemmatimonas and Sphingomonas, by T32781 inoculation, which potentially contributed to the restoration of plant growth under Cd exposure. In summary, our study demonstrated that T. nigricans T32781 effectively alleviated Cd stress in tobacco plants by reducing Cd uptake, alleviating Cd-induced oxidative stress, influencing plant metabolite and modulating the microbial composition in the rhizosphere. These findings offer a novel perspective and a promising candidate strain for enhancing Cd tolerance and prohibiting its accumulation in plants to reduce health risks associated with exposure to Cd-contaminated plants.

Cadmium exposure is associated with chronic kidney disease in a superfund site lead smelter community in Dallas, Texas.

Background: The study was conducted in a Dallas lead smelter community following an Environmental Protection Agency (EPA) Superfund Cleanup project. Lead smelters operated in the Dallas community since the mid-1930s.Aim: To test the hypothesis that cadmium (Cd) exposure is associated with chronic kidney disease (CKD) ≥ stage 3.Subjects and methods: Subjects were African American residents aged ≥19 to ≤ 89 years (n=835). CKD ≥ stage 3 was predicted by blood Cd concentration with covariates.Results: In logistic regression analysis, CKD ≥ stage 3 was predicted by age ≥ 50 years (OR = 4.41, p < 0.0001), Cd level (OR = 1.89, p < .05), hypertension (OR = 3.15, p < 0.03), decades living in the community (OR = 1.34, p < 0.003) and T2DM (OR = 2.51, p < 0.01). Meta-analysis of 11 studies of Cd and CKD ≥ stage 3 yielded an ORRANDOM of 1.40 (p < 0.0001). Chronic environmental Cd exposure is associated with CKD ≥ stage 3 in a Dallas lead smelter community controlling covariates.Conclusion: Public health implications include screening for heavy metals including Cd, cleanup efforts to remove Cd from the environment and treating CKD with newer renal-sparing medications (e.g., SGLT-2 inhibitors, GLP-1s).

Indigenous earthworms and gut bacteria are superior to chemical amendments in the remediation of cadmium-contaminated seleniferous soils.

The natural selenium (Se)-rich areas in China are generally characterized by high geological background of cadmium (Cd) which poses potential risks to human health. Therefore, immobilization of Cd is the prerequisite to ensure the safe utilization of natural seleniferous soil resources. A pot experiment was conducted to compare the effects of indigenous earthworm (Amynthas hupeiensis) and its gut bacteria (Citrobacter freundii DS strain) on the remediation of Cd-contaminated seleniferous soil with two traditional chemical amendments. The results indicated that earthworms and DS strain decreased DGT-extractable Cd by 25.52 - 41.53% and reduced Cd accumulation in lettuce leaves by 20.83 - 37.50% compared with control through converting the exchangeable Cd (EX-Cd) into residual Cd (RE-Cd) fractions. Overall, earthworms and DS strain were more effective in Cd immobilization, growth and quality promotion, oxidative stress alleviation, Cd accumulation and bioaccessibility reduction in the soil-lettuce-human continuum than biochar and lime. Moreover, all amendments induced the antagonism between Se and Cd through increasing bioavailable Se/Cd molar ratios in soil. However, all the Cd concentrations in lettuce exceeded the maximum permissible limit of Cd for leaf vegetables, indicating that soil amendment alone could not ensure food safety. This study confirmed that biological amendments were superior to chemical amendments in the remediation of Cd-contaminated seleniferous soil.

Foliar spray with rutin improves cadmium remediation efficiency excellently by enhancing antioxidation and phytochelatin detoxification of Amaranthus hypochondriacus.

Rutin is a flavonoid with strong antioxidative effects on plant metabolism that facilitates resistance to environmental stress. The effect of foliar rutin on cadmium (Cd) uptake in Amaranthus hypochondriacus (K472) was studied. The results showed that a foliar spray of rutin alleviated Cd toxicity, promoted plant growth, improved Cd transfer to and storage in aerial plant parts and Cd accumulation with positive effects over time. A rutin concentration of 1.5 mg/mL showed the strongest promotion effect: the biomass and Cd content were increased at 13 days by 68.62% and 405.54% compared to 3 days, respectively, whereas a high concentration of rutin (5 mg/mL) inhibited plant growth and hindered Cd absorption. Two stages of Cd detoxification were identified in K472 after appropriate rutin application. First, an antioxidant system including an enzymatic antioxidant (superoxide dismutase [SOD]) and nonenzymatic antioxidants (glutathione [GSH] and flavonoids) was activated to enhance plant stress resistance. Quercetin and phytochelatin (PC) synthesis were then enhanced to perform detoxification synergistically with the antioxidant system to improve stress tolerance and achieve stable Cd detoxification. The results demonstrated that appropriately prolonging the application time of exogenous rutin to K472 is an effective way to improve the Cd remediation efficiency.

The application of exogenous rutin to regulate the growth and Cd absorption of grain amaranth is reported for the first time. A foliar spray of rutin enriches Cd by regulating the metabolism of flavonoids and enhancing antioxidation and phytochelatin detoxification under Cd stress. Properly prolonging the harvest time after rutin treatment can greatly improve the Cd remediation efficiency of soil. The findings of the present study would be helpful for the remediation of Cd-contaminated soils.

Role of Heavy Metals in Diabetes: Mechanisms and Treatment Strategies.

Toxic metals affecting metabolic pathways have a broad range in the ecosystem from both natural and anthropogenic sources. Because of constant contamination from waste and untreated chemical effluents, their emissions have risen significantly over the last few decades, quickly gaining attention due to their crucial role in the development of several metabolic disorders, notably diabetes mellitus. Cadmium and arsenic not only spread widely in our atmosphere but are also linked to a wide range of health hazards. These are primarily accumulated in the liver, kidney, and pancreas once they reach the human body, where they have deleterious effects on the metabolism of glucose and its association with other metabolic pathways, particularly glycolysis, glycogenesis, and gluconeogenesis, by altering and impairing the specific activity of major enzymes. Impairment of hepatic glucose homeostasis plays a crucial role in diabetes mellitus pathogenesis. Impaired liver and kidney functions, as well as decreased pancreatic and muscle function, also contribute significantly to elevated levels of blood glucose. Heavy metals have the potential to cause changes in the conformation in these enzymes. They also impair hormonal balance by destroying the pancreas and adrenal glands. Such metals often facilitate the development of reactive oxygen species and inhibit antioxidant defense mechanisms, with multiple organs subsequently damaged. This review briefly discusses the involvement of heavy metals in metabolic disorders such as diabetes mellitus, the enzymes involved in this pathway, and glucose homeostasis.

Dynamics of Soil Microbial N-Cycling Strategies in Response to Cadmium Stress.

Globally increasing trace metal contamination of soils requires a better mechanistic understanding of metal-stress impacts on microbially mediated nutrient cycling. Herein, a 5-month laboratory experiment was employed to assess the effects of cadmium (Cd) on soil microbial N-cycling processes and associated functional gene abundance, with and without urea amendment. In non-N-amended soils, Cd progressively stimulated microbial populations for N acquisition from initial dissolved organic N (DON) to later recalcitrant organic N. The acceleration of N catabolism was synchronously coupled with C catabolism resulting in increased CO2/N2O fluxes and adenosine triphosphate (ATP) contents. The abundance of microbes deemed inefficient in N catabolism was gradually repressed after an initial stimulation period. We posit that enhanced exergonic N processes diminished the need for endergonic activities as a survival strategy for N communities experiencing metal stress. With urea amendment, Cd exhibited an initial stimulation effect on soil nitrification and a later a promotion effect on mineralization, along with an increase in the associated microbial populations. In N-amended soils, Cd accelerated N/C transformation processes, but decreased N2O and CO2 fluxes by 19 and 14%, respectively. This implies that under eutrophic conditions, Cd synchronously altered microbial C/N metabolism from a dominance of catabolic to anabolic processes. These results infer a nutrient-based adjustment of microbial N-cycling strategies to enhance their metal resistance.

Caffeine versus antioxidant combination (Antox) and their role in modifying cadmium-induced testicular injury in adult male albino rats.

The aim of the current work was to compare the roles of caffeine and antioxidants in prevention of cadmium-induced testicular damage when given, in addition to cadmium, in adult male albino rats. Histopathological and ultra-structural examination as well as biochemical and molecular assessments were done. Cadmium chloride (4 mg/kg body weight) was administered via oral gavage from day 21 to 28 of the experiment. Caffeine (25 mg/kg) via intra-peritoneal injection and antioxidant preparation (Antox) 10 mg/kg via oral gavage were given as a pre-treatment for 21 days and concomitantly with Cd from day 21 to 28. Real-time PCR was done for determination of 3, 17 ß hydroxy steroid dehydrogenase steroidogenic acute regulatory protein, caspase-9 and mitofusin 1,2 gene expression. Testosterone level, glutathione S-transferase enzyme activity, reactive oxygen species, malondialdehyde and superoxide dismutase were measured spectrophotometrically by ELISA. Histological and ultra-structural evaluation revealed disturbance of normal architecture, vacuolisation and necrosis. Vascular dilatation and congestion and collagen fibre deposition were present. A statistically significant difference was seen in all parameters when caffeine and antioxidants were given against cadmium-induced testicular injury. Overall, we conclude that both caffeine and antioxidants have the ability to reverse cadmium-induced testicular injury when given as pre-treatment prior to cadmium exposure.

Cadmium-induced phytotoxicity and tolerance response in the low-Cd accumulator of Chinese cabbage (Brassica pekinensis L.) seedlings.

In vegetable production, Chinese cabbage can readily accumulate cadmium (Cd) into its edible parts and exceed food safety standards. However, there are still some ecotypes that respond differently to cadmium stress. This study aimed to investigate the differences of Cd-induced (0, 10, 50, 100, 200 µM) response under hydroponic culture between two Chinese cabbage ecotypes which were promoted in northeastern China from the characteristics of biomass, uptake kinetic, accumulation, and initial oxidative stress. In this paper, it was confirmed that Jinfeng (JF) was a Cd-tolerant cultivar and had low Cd accumulation in edible part, while Qiutian (QT) was Cd-sensitive, exhibiting a faster Cd uptake rate but lacking effective Cd detoxication mechanisms, and was severely damaged by 10 µM Cd treatment. Conversely, even at a high Cd concentration of 200 µM, Jinfeng had weaker biomass inhibition, lower root Cd affinity, more difficult root-to-leaf translocation, and stronger antioxidant enzyme activity than Qiutian. In conclusion, Jinfeng can endure mild Cd stress (<10 µM), and Qiutian can be used as a Cd indicator. This study provides reliable materials and related data support for vegetable production in areas with mild Cd pollution.Novelty statement: This work further investigates the unique features of low-Cd accumulator in Chinese cabbage (Brassica pekinensis L.) seedlings as an interesting material for vegetable production in areas with mild Cd pollution. It also explains the differences between Cd-tolerant and Cd-sensitive cultivars under different cadmium stress levels and how these differences can alter their response. With the increase of Cd concentration, Cd-tolerant cultivars compared to Cd-sensitive cultivars showed less biomass decrease, lower accumulation, lower TF, more chemically stable Cd in roots and more active antioxidant enzymes under the same Cd stress level. With the development of seedlings, the uptake of Cd in roots and the translocation to the leaves were effectively restricted by the poor Cd affinity of roots, the conversion of Cd chemical forms and the promotion of antioxidase activities, in a Cd-tolerant low accumulator, Jinfeng.

Performance of Actinobacteria isolated from rhizosphere soils on plant growth promotion under cadmium toxicity.

This work aimed to evaluate the potential use of plant growth-promoting actinobacteria (PGPA) for enhanced cadmium (Cd) phytoremediation and plant growth. Forty-two actinobacteria were isolated from rhizosphere soils in Thailand. Among isolates tested, only Streptomyces phaeogriseichromatogenes isolate COS4, showed the high ability to produce siderophores as a plant growth stimulant and had a strong Cd tolerance potential. The significance of siderophores production and Cd tolerance ability under different Cd concentrations suggests the potential of isolate COS4 to work effectively. Plant culture revealed that the significant increase in root length, root to tip length, and total dried weight of sunflower were obtained after 2 h incubation of sunflower seeds with isolate COS4. The efficiency of Cd uptake was found to range between 42.3 and 61.3%. Translocation factor results confirmed that plant growth promoting S. phaeogriseichromatogenes isolate COS4-assisted phytoremediation can be considered as Cd absorbents for the restoration of polluted sites due to high translocation values.

Enhanced biomass and cadmium accumulation by three cadmium-tolerant plant species following cold plasma seed treatment.

Cold plasma seed treatment can promote plant growth and enhance the resistance of agricultural crops to adverse stress. However, the effects of plasma seed treatment on the growth and phytoextraction response of plants to cadmium (Cd) remain poorly documented. Here, we have investigated the feasibility of using plasma seed treatment to enhance the biomass and Cd accumulation of three Cd-tolerant species, namely Bidens pilosa L, Solanum nigrum L. and Trifolium repens L, under different plasma treatment conditions. Possible enhancement mechanisms are also proposed according to the levels of organic acids in the roots and the Cd fractions in rhizosphere soil following different plasma treatment conditions. The optimum plasma power was 100 W (B. pilosa) or 500 W (S. nigrum and T. repens). The optimum plasma exposure time for all three species was 60 s. Plasma seed treatment under the optimum treatment conditions enhanced plant dry biomass by ~17.3-45.0% and Cd accumulation by 8.8-54.4% across all three species compared to the controls. Furthermore, the phytoremediation efficiencies, bioaccumulation factors and transfer factors of the three species also increased significantly after seed plasma treatment. The promotion of plasma treatment on the biomass and Cd accumulation of three species might be due to increased exudation of organic acids from the roots into the rhizosphere soil, thus increasing the concentrations of acid-soluble Cd to form Cd-organic acid complexes that facilitated the uptake and translocation of Cd by the plants. Results of this study revealed that cold plasma seed treatment is an environmentally friendly, economical and efficient means to develop the application of phytoremediation for Cd-contaminated soils.

Microbial Sensing and Removal of Heavy Metals: Bioelectrochemical Detection and Removal of Chromium(VI) and Cadmium(II).

The presence of inorganic pollutants such as Cadmium(II) and Chromium(VI) could destroy our environment and ecosystem. To overcome this problem, much attention was directed to microbial technology, whereas some microorganisms could resist the toxic effects and decrease pollutants concentration while the microbial viability is sustained. Therefore, we built up a complementary strategy to study the biofilm formation of isolated strains under the stress of heavy metals. As target resistive organisms, Rhizobium-MAP7 and Rhodotorula ALT72 were identified. However, Pontoea agglumerans strains were exploited as the susceptible organism to the heavy metal exposure. Among the methods of sensing and analysis, bioelectrochemical measurements showed the most effective tools to study the susceptibility and resistivity to the heavy metals. The tested Rhizobium strain showed higher ability of removal of heavy metals and more resistive to metals ions since its cell viability was not strongly inhibited by the toxic metal ions over various concentrations. On the other hand, electrochemically active biofilm exhibited higher bioelectrochemical signals in presence of heavy metals ions. So by using the two strains, especially Rhizobium-MAP7, the detection and removal of heavy metals Cr(VI) and Cd(II) is highly supported and recommended.

Metabolomics reveals the "Invisible" detoxification mechanisms of Amaranthus hypochondriacus at three ages upon exposure to different levels of cadmium.

To decipher the Cd hyperaccumulation and tolerance mechanisms of plants and increase phytoremediation efficiency, in this study, the physiological effects induced by environmentally relevant concentrations (0, 25 and 200 mg/kg) of Cd were characterized in Amaranthus hypochondriacus (K472) at three growth stages using LC/MS-based metabolomics. Metabolomic analysis identified 31, 29 and 30 significantly differential metabolites (SDMs) in K472 exposed to Cd at the early, intermediate and late stages of vegetative growth, respectively. These SDMs are involved in nine metabolic pathways responsible for antioxidation, osmotic balance regulation, energy supplementation and the promotion of metabolites that participate in phytochelatin (PC) synthesis. K472 at the intermediate stage of vegetative growth had the strongest tolerance to Cd with the combined action of Ala, Asp and Glu metabolism, purine metabolism, Gly, Ser and Thr metabolism and Pro and Arg metabolism. Among these crucial metabolic biomarkers, purine metabolism could be the primary regulatory target for increasing the Cd absorption of K472 for the restoration of Cd-contaminated soil.

Promotion of growth and phytoextraction of cadmium and lead in Solanum nigrum L. mediated by plant-growth-promoting rhizobacteria.

Plant growth-promoting rhizobacteria (PGPR) are a specific category of microbes that improve plant growth and promote greater tolerance to metal stress through their interactions with plant roots. We evaluated the effects of phytoremediation combining the cadmium accumulator Solanum nigrum L. and two Cd- and Pb-resistant bacteria isolates. To understand the interaction between PGPR and their host plant, we conducted greenhouse experiments with inoculation treatments at Nanjing Agricultural University (Jiangsu Province, China), in June 2018. Two Cd- and Pb-resistant PGPR with various growth-promoting properties were isolated from heavy metal-contaminated soil. 16S rRNA analyses indicated that the two isolates were Bacillus genus, and they were named QX8 and QX13. Pot experiments demonstrated that inoculation may improve the rhizosphere soil environment and promote absorption of Fe and P by plants. Inoculation with QX8 and QX13 also enhanced the dry weight of shoots (1.36- and 1.7-fold, respectively) and roots (1.42- and 1.96-fold) of plants growing in Cd- and Pb-contaminated soil, and significantly increased total Cd (1.28-1.81 fold) and Pb (1.08-1.55 fold) content in aerial organs, compared to non-inoculated controls. We also detected increases of 23% and 22% in the acid phosphatase activity of rhizosphere soils inoculated with QX8 and QX13, respectively. However, we did not detect significant differences between inoculated and non-inoculated treatments in Cd and Pb concentrations in plants and available Cd and Pb content in rhizosphere soils. We demonstrated that PGPR-assisted phytoremediation is a promising technique for remediating heavy metal-contaminated soils, with the potential to enhance phytoremediation efficiency and improve soil quality.