High Concentrations Of Cd2 Research Articles

The effect of cadmium on a semi-self-sustaining microalgal-bacterial granular sludge process for wastewater treatment

Microalgal-bacterial granular sludge (MBGS) is an innovative and sustainable technology for wastewater treatment. This research investigated the effect of Cd2+ on the performance and characteristics of such semi-self-sustaining MBGS reactors (with additional intermittent aeration). After 30 days of exposure to 0, 2, and 10 mg·l−1 Cd2+, the three reactors consistently exhibited robust removal efficiencies, achieving 89 % removal for chemical oxygen demand (COD) and 99 % removal for NH4+-N. However, the MBGS in control exhibited better performance in T-N removal compared to MBGS exposed to 10 mg·l−1 Cd2+ (especially during the light phase), indicating a potential impact of Cd2+ on the N-assimilation process of microalgae. The high concentration of Cd2+ also negatively affected the MBGS structure and increased the production of extracellular polymeric substances. Further investigations of the dissolved oxygen profile were conducted under phototrophic conditions, the maximum oxygen production rate contributed to microalgae in the control group was 20.9 % and 46.4 % higher than that of groups with 2 and 10 mg·l−1 Cd2+. The results show that Cd2+ mainly impacts the microalgae in the outer layer of the structure, and additional aeration helps compensate for the decrease in oxygen production caused by Cd2+ in MBGS, thereby making the system more stable in removing COD and NH4+-N.

Cadmium-Induced Physiological Responses, Biosorption and Bioaccumulation in Scenedesmus obliquus.

Cadmium ion (Cd2+) is a highly toxic metal in water, even at low concentrations. Microalgae are a promising material for heavy metal remediation. The present study investigated the effects of Cd2+ on growth, photosynthesis, antioxidant enzyme activities, cell morphology, and Cd2+ adsorption and accumulation capacity of the freshwater green alga Scenedesmus obliquus. Experiments were conducted by exposing S. obliquus to varying concentrations of Cd2+ for 96 h, assessing its tolerance and removal capacity towards Cd2+. The results showed that higher concentrations of Cd2+ (>0.5 mg L-1) reduced pigment content, inhibited algal growth and electron transfer in photosynthesis, and led to morphological changes such as mitochondrial disappearance and chloroplast deformation. In this process, S. obliquus counteracted Cd2+ toxicity by enhancing antioxidant enzyme activities, accumulating starch and high-density granules, and secreting extracellular polymeric substances. When the initial Cd2+ concentration was less than or equal to 0.5 mg L-1, S. obliquus was able to efficiently remove over 95% of Cd2+ from the environment through biosorption and bioaccumulation. However, when the initial Cd2+ concentration exceeded 0.5 mg L-1, the removal efficiency decreased slightly to about 70%, with biosorption accounting for more than 60% of this process, emerging as the predominant mechanism for Cd2+ removal. Fourier transform infrared correlation spectroscopy analysis indicated that the carboxyl and amino groups of the cell wall were the key factors in removing Cd2+. In conclusion, S. obliquus has considerable potential for the remediation of aquatic environments with Cd2+, providing algal resources for developing new microalgae-based bioremediation techniques for heavy metals.

Mechanistic Insight Into Cadmium- and Zinc-Induced Inactivation of the Candida albicans Pif1 Helicase.

Zinc and cadmium are environmental contaminants that can cause disease by affecting the activity of DNA-repair proteins. In this study, we investigated the effect of Zn2+ and Cd2+ on the Candida albicans Pif1, a DNA-repair helicase that plays a critical role in ensuring genomic stability. We show that Zn2+ and Cd2+ strongly inhibit both the ATPase and the unwinding activities of CaPif1, but have no effect on its DNA binding activity. High concentrations of Cd2+ may bind to the cysteine residues of CaPif1, and its inhibition appears to be difficult to be restored by ethylene diamine tetraacetic acid, while inhibition due to Zn2+ can. When the two ions are at low concentrations, increasing the concentration of ATP in the reaction can appropriately weaken the inhibitory effect of Zn2+, while cysteine can reduce the inhibitory effect of Cd2+. In addition, we found that for both Cd2+ and Zn2+ the inhibition effects were nearly 100 times greater in reduced environments than in non-reducing environments. When heavy metals stimulate the body’s response, the environment of the body becomes less reducing, and thus the tolerance of CaPif1 to heavy metals will be stronger. We propose that CaPif1 may resist the toxicity of heavy metals through this mechanism. Altogether, our results provide new insights into the mechanisms by which heavy metals are toxic to DNA-repair proteins.

Physiological Responses of Ryegrass in Cadmium-Nonylphenol Co-contaminated Water and the Phytoremediation Effects

Physiological responses of ryegrass in cadmium-nonylphenol (Cd-NP) co-contaminated water, as well as the phytoremediation effect were studied under laboratory conditions. The experiment revealed that the biomass and chlorophyll content of ryegrass significantly declined at high concentrations of Cd2+(10 mg·L-1), while POD and PPO activities significantly increased. No significant changes to the biomass, chlorophyll content and MDA of ryegrass were observed in the presence of NP. POD activities significantly increased at high concentrations of NP (5 mg·L-1). The addition of high NP concentrate reduced the inhibition of Cd under co-contaminated stress, the MDA content and PPO activities both reduced. The experiment also revealed that the removal rate of Cd2+ by ryegrass reached 55.3% after 12 h. The absorption efficiency was improved by high NP concentration. Absorption efficiency of Cd2+ by the subterranean part of the plant significantly increased in presence of NP, and the absorption efficiency increased with the increase of NP concentration. The absorption rate of NP was 44.6% after 24 h at NP concentration of 5 mg·L-1. The removal rate was slightly influenced at low concentrations of Cd2+, but significant inhibition of absorption and degradation was observed at high concentrations of Cd2+.

Inhibitory effect of cadmium(II) ion on anodic electrochemically active biofilms performance in bioelectrochemical systems

Cadmium(II) ion can affect the anode performance of bioelectrochemical systems (BES); however, how the presence of Cd2+ affect the extracellular electron transfer of anodic electrochemically active biofilms (EABs), the microbial viability and species composition of microorganism on the anode remain poorly understood. Here, we investigated the inhibitory effect of Cd2+ at different concentrations on the electrochemical performance and the biofilm community in mixed-culture enriched BES. The electrochemical performance of the BES was not inhibited at 2 mg L−1 Cd2+, while higher concentrations of 5–20 mg L−1 resulted in the decrease in the maximum power density, with 0.34 ± 0.01 W m−2 at 5 mg L−1, 0.28 ± 0.01 W m−2 at 10 mg L−1, and 0.17 ± 0 W m−2 at 20 mg L−1, respectively. When adding 30 mg/L Cd2+, there was almost no power output. The decline of the power output was possibly ascribed to the suppressed viability and the change of species richness as evident from confocal laser scanning microscopy and microbial community analysis. Cyclic voltammogram and electrochemical impedance spectroscopy revealed that high concentration of Cd2+ exceeding 5 mg L−1 can inhibit the secretion of outer membrane cytochromes, thus reducing the electron transfer between the EABs and the anode surface. Analysis of bacterial structures showed a decrease in Geobacter accompanied by an increase in Stenotrophomonas and Azospira in response to Cd2+ at 10 and 20 mg L−1. This study added to the in-depth analysis of the inhibition of Cd2+ on EABs, and provided new insights into the removing Cd2+ and organics simultaneously in BES.

Inhibition of biofilm formation by Cd2+ on Bacillus subtilis 1JN2 depressed its biocontrol efficiency against Ralstonia wilt on tomato

Bacillus subtilis 1JN2 can serve as an effective biocontrol agent against Ralstonia wilt on tomato, but the efficiency of control depends on the levels of heavy metals in the rhizosphere soil. Here, we investigated how the heavy metal Cd2+ affects the biocontrol efficacy of B.subtilis 1JN2 on Ralstonia wilt. We found that low Cd2+ content of 2 mM or lower had no effects on the biofilm formation of 1JN2, while media containing 3 mM or higher Cd2+ levels inhibited biofilm formation. Interestingly, high concentration of Cd2+ (5 mM) showed inhibition of B.subtilis 1JN2 cell growth. We next tested the effects of Cd2+ on the colonization of 1JN2 by supplementing artificial Cd2+ in the tomato rhizosphere in a greenhouse setting. We found that 3 mM Cd2+ in the tomato rhizosphere inhibited the colonization of B.subtilis 1JN2, Only 103 CFU/mL 1JN2 was detected one week post treated with 107 CFU/mL but 105 CFU/mL could be detected without Cd2+ in the soil. The presence of Cd2+ had no effect on the colonization of Ralstonia solanacearum on tomato, but the biocontrol efficacy against Ralstonia wilt by 1JN2 decreased 54.2% when the soil contained 3 mM Cd2+ compared to the control without Cd2+. Taken together, we found that the failure of biofilm formation of Bacillus subtilis 1JN2 that affected by Cd2+ lead to the decrease of its biocontrol efficacy against Ralstonia wilt on tomato.

Toxic effects of cadmium on tall fescue and different responses of the photosynthetic activities in the photosystem electron donor and acceptor sides

Tall fescue (Festuca arundinacea Schreb) is a turf grass species which is widely used for rhizoremediation of organic contaminants and shows notable prospects in heavy metal phytoremediation. In this study, different concentrations of cadmium ion (Cd2+) were applied to study toxic effects of Cd2+ and responses of tall fescue by soilless culture. Tall fescue showed comparable high tolerance to Cd2+ as Indian mustard (Brassica juncea L.). Additionally, the treatment with high concentration of Cd2+ leaded to decreased chlorophyll contents, production of reactive oxygen species (ROS) and lipid peroxidation, as well as damage of cell membrane, necrosis and apoptosis in tall fescue roots, and toxicity of Cd2+ on physiologic properties of tall fescue has been well discussed. Moreover, in photosystem II electron donor side, electron transport from oxygen evolution complex (OEC) to Yz residue of D1 protein was inhibited under high Cd2+ treatments, which may be due to the Cd2+ induced ROS production and the replacement of Ca2+ in the core of OEC. In electron acceptor side, electron transport efficiency from quinone B to photosystem I acceptors increased under high Cd2+ treatments, which may be an important response for plants against Cd2+ toxicity and its mechanism needs our further study.

Photoelectrochemical biosensor for acetylcholinesterase activity study based on metal oxide semiconductor nanocomposites

Acetylcholinesterase (AChE) is a well-known serine hydrolase and its dysfunction could disturb cholinergic neurotransmission which is related to the pathogenesis of neurodegenerative disorders. In this report, a photoelectrochemical biosensor based on metal oxide semiconductor nanocomposite was fabricated to investigate the effect of cadmium ion (Cd2+) on the activity of AChE. The photoelectrochemical nanocomposite was prepared by anodic oxidation of titanium (Ti) foil to form titanium dioxide (TiO2) nanotubes (TNs) array followed by cathodic deposition of zinc oxide nanorods (ZnONRs) onto the TNs. AChE was immobilized on the obtained nanocomposites and the biosensor showed enhanced photoelectrochemical response under visible light irradiation. The experimental results showed that Cd2+ exhibited interesting dose-dependent and time-dependent effects on AChE activity. Specifically, high concentration of Cd2+ inhibited while low level of Cd2+ could stimulate the activity of AChE. These findings are of great significance for the study of enzyme activity influenced by metal ions and related pathogenesis investigation of neurodegenerative disorders.

A combined biological removal of Cd2+ from aqueous solutions using Phanerochaete chrysosporium and rice straw

The removal of Cd2+ from aqueous solutions by agricultural residues rice straw combined with white rot fungus Phanerochaete chrysosporium (P. chrysosporium) was investigated. The results showed that over 99% of the total Cd2+ (initial concentration of 150mgL−1) was removed at the optimal operating conditions (pH 5.0 at 35°C). We also found that P. chrysosporium could survive under Cd2+ stress even with an initial Cd2+ concentration of 250mgL−1. But when Cd2+ concentration increased to 250mgL−1, fungus growth and reproduction were remarkably restrained, and as a result, Cd2+ removal dropped to 59.2%. It was observed that the fungus biomass and activities of ligninolytic enzymes decreased at some degree under high concentration of Cd2+ (above 100mgL−1). Also, we found that a moderate Cd2+ stress (below 150mgL−1) could stimulate P. chrysosporium's production of the heavy metals chelator - oxalate. This study will provide useful information for the application of biological removal of heavy metal irons from wastewater.

Influence of Cd2+ on Growth and Chlorophyll Fluorescence in a Hyperaccumulator: Lonicera japonica Thunb.

Chlorophyll fluorescence is an important instrument to study the responses of plants to cadmium (Cd) stress, which in turn can provide a better understanding of Cd tolerance in plants. In the present study, the influence due to cadmium (Cd2+) exposure on growth and chlorophyll fluorescence was investigated in a new hyperaccumulator—Lonicera japonica Thunb. Four levels of Cd2+ (0, 5, 25, and 125 mg kg−1) were added to the soil. After 90 days of Cd2+ exposure, maximal photochemical efficiency of photosystem II (F v/F m) and effective quantum yield of photosystem II (ΦPS II) of L. japonica showed an increase under 5 mg kg−1 Cd2+ exposure, but decreased under higher concentrations of Cd2+exposure. However, when Cd concentrations in soil were up to the highest concentrations (125 mg kg−1), no significant differences of F v/F m, ΦPS II, photochemical quenching, chlorophyll, and carotenoid contents compared with the control were observed. These results indicate that the good tolerance of L. japonica to Cd might result from effective mechanisms including the capacity to maintain good growth, photosynthetic pigment composition, and chlorophyll fluorescence activity, which would be beneficial to enhance the potential for phytoremediation.

Photocatalytic degradation of gaseous benzene with CdS-sensitized TiO2 film coated on fiberglass cloth

In this paper, TiO2 film coated on fiberglass cloth was synthesized by sol–gel method and further sensitized by CdS nanoparticles using a sequential chemical bath deposition technique. Gaseous benzene was adopted as a model pollutant to evaluate the photocatalytic performances of the supported TiO2 films sensitized with variable content of CdS nanoparticles, which obtained by adjusting the concentration of Cd2+ or S2− precursor solution. Along with the increase of the CdS amount, the photocatalytic activity of these samples initially increases and then shows a downward trend. When the concentration of Cd2+ or S2− precursor solution achieved 0.005M, the sample performs the best photocatalytic property and the degradation efficiency reaches 92.8% and 32.7% under UV–vis and visible light irradiation, respectively. The enhancement of the photocatalytic activity could be attributed to the formation of micro-heterojunction. However, a thick CdS sheath covered catalyst surface will form when high concentration of Cd2+ or S2− solution is used. The low photogenerated electron–hole pairs separation efficiency and the photocorrosion process of CdS decrease the photocatalytic activity gradually.

Spectroscopic and Microscopic Studies on the Mechanisms of Mitochondrial Toxicity Induced by Different Concentrations of Cadmium

The deleterious action of Cd2+ on rat liver mitochondria was investigated in this work using spectroscopic and microscopic methods. The concentration dependence of Cd2+ on mitochondrial swelling, membrane potential and membrane fluidity was studied. Our aim was to detect the active sites of Cd2+ in the mitochondrial membrane treatments with cyclosporin A (CsA) and EGTA on the mitochondrial permeability transition (MPT) induced by low and high concentrations of Cd2+. The protective effects of dithiothreitol, human serum albumin and monobromobimane+ on Cd2+-induced MPT were also monitored. All of these investigations indicated that Cd2+ can directly affect MPT at two separate localization sites at different concentrations: the classic Ca2+ triggering site and the thiol (-SH) groups of membrane proteins matched by MPT pore opening (defined as "S" site). At the high concentration of Cd2+, other free -SH groups in the mitochondrial matrix may be involved in this process. These findings were supported by transmission electron microscopy and shed light on the toxic mechanism of Cd2+ on mitochondria.

Alleviation of cadmium toxicity on maize seedlings by calcium

The rate of germination, radicle and plumule length, fresh and dry mass of maize seedlings were increased as Ca2+ was added to the nutrient solution, which contained different levels of Cd2+, especially at low concentration of Ca2+ (5 mM) and high concentrations of Cd2+ (1.4 and 1.8 mM). The biosynthesis of pigments, respiration rate and content of soluble saccharides in endosperm were reduced sharply as the concentration of Cd2+ in the medium increased. This effects was alleviated by Ca2+ addition. Cd2+ content in seedlings was increased as the Cd2+ concentration in medium was increased and decreased sharply as Ca2+ was present in the culture medium. The study suggests liming of soil with CaCO3 to improve the yield of many crops.

Low- and high-voltage-activated calcium currents in rat spinal dorsal horn neurons

1. Calcium currents in immature rat spinal dorsal horn neurons in transverse slices were studied with the single-electrode voltage-clamp technique. Using experimental conditions that minimized voltage-dependent Na+ and K+ currents, we distinguished low- and high-voltage-activated calcium currents on the basis of their voltage dependence and sensitivity to the Ca2(+)-channel agonist and antagonist drugs. 2. The low-voltage-activated transient calcium current is evoked with weak depolarizing voltage commands. It begins to activate at potentials positive to -70 mV and increases in amplitude and rate of decay with depolarization, the peak values being reached between -40 and -30 mV. The current is fully activated at a holding potential of about -110 mV. Steady-state inactivation is complete at potentials in the range of -60 to -50 mV. 3. The transient component of the high-threshold calcium current appears at membrane potentials close to -40 mV and slowly decays within several hundreds of milliseconds. The amplitude of the current increases with more negative holding potentials (-100 to -40 mV). 4. The sustained component of the high-threshold calcium current seems to activate at potentials positive to -40 mV and exhibits little inactivation during 0.3- to 0.5-s depolarizing commands. This component is better isolated at more depolarized holding potentials (between -40 and -30 mV) that inactivate the transient components of the low- and high-threshold calcium currents. 5. A rundown of calcium currents was seen in dorsal horn cells. The time stability of the transient and sustained components of the high-threshold calcium current was lower than that of the low-threshold transient current. The latter current seemed to be insensitive up to 1 h. 6. (-)-Bay K 8644 (1-10 microM), a dihydropyridine agonist, enhanced the high-threshold calcium current, in particular the sustained component, but not the transient low-threshold calcium current. The dihydropyridine antagonist nifedipine (5-50 microM) selectively reduced the sustained component of the high-threshold calcium current while having little or no effect on the transient components of the low- and high-threshold calcium currents. 7. Cadmium ions (60-100 microM) and cobalt ions (2 mM) markedly reduced both components of the high-threshold calcium current, and Cd2+ only slightly decreased the low-threshold transient current. However, all three components are indiscriminately blocked by higher concentrations of Cd2+ and Co2+.(ABSTRACT TRUNCATED AT 400 WORDS)