Effects of multi-walled carbon nanotubes in soil on earthworm growth and reproduction, enzymatic activities, and metabolomics

Toxicological evaluation and metabolic profiling of earthworms (Eisenia fetida) after exposure to microplastics and acetochlor

In recent years, microplastic (MPs) and pesticide pollution have become prominent issues in the field of soil pollution. This research endeavored to assess the impact of ultraviolet radiation (UV) on the characteristics of microplastics, as well as investigating the toxicological effect on earthworms (Eisenia fetida) when subjected to the dual stressors of microplastics and acetochlor (ACT). This research found that microplastics aged under UV were more prone to wear and tear in the environment, and produced more oxygen-containing functional groups. Chronic exposure experiments were conducted on ACT and aged-MPs. The results revealed that aged-MPs and ACT inhibited earthworm growth, induced oxidative stress, and caused damage to both the body cavity muscles and the intestinal lumen. Compared with individual exposure, combined exposure increased the oxidative products (superoxide dismutase (SOD) and catalase (CAT)) and altered the expression levels of related genes (TCTP and Hsp70) significantly. PE inflicted more significant harm to the earthworm intestinal tissue compared to PBAT. By 1H-NMR metabolomics, the investigation delved into the repercussions of PE and ACT on the metabolic pathways of earthworms. Exposure to ACT and PE can disrupt the stability of intestinal membranes stability, amino acid metabolism, neuronal function, oxidative stress and energy metabolism. Overall, the research revealed that combined exposure of MPs and ACT exacerbated the negative effects on earthworms significantly, and contributed valuable insights to environmental risk assessment of the combined toxicity of microplastics and pesticides.

Carbon-based nanocarriers for plant growth promotion: fuelling when needed

Climate change (i.e., rising temperature and precipitation) due to global warming is affecting soil fertility, thereby significantly causing a decrease in agriculture production worldwide. At the same time, increasing demands for food supplies with the growing global population puts extra pressure to improve agricultural production. Indeed, chemical fertilizers and pesticides are a great help in fuelling agro-production, but their excess use could deteriorate the environment and human health. Nevertheless, nanomaterials, especially carbon-based nanostructured materials (CB-NMs), have revolutionized the agricultural sector in various ways including the on-demand supply of essential nutrients, biomolecules, and growth factors to plants. Carbon nanofibers (CNFs) are one such example that can be tuned to carry essential nutrients (i.e., Fe, Cu, Zn, and Mo) and deliver to plants when and what is in need. As a result, it not only improves the crop yield but also maintains the nutritional quality (protein, carbohydrate, and mineral contents) of plant products. This review discusses the most innovative development in CB-NM-based carriers (CNFs, carbon nanotubes (CNTs), and graphene as well as its derivatives) for plant growth applications including the approaches being used for their lab-scale synthesis. In addition, their application as the carrier of micronutrients and biomolecules and the successful delivery (and the underlying mechanism) of genes, nucleic acids, microbes, and their components in plants are discussed.

Fomesafen induced ecotoxicological responses, bioaccumulation, and implications for soil ecosystems remediation in three ecotypes earthworms

Fomesafen (FSA) is a herbicide commonly used in soybean fields, but its long half-life in the soil can pose pollution risks to the soil ecosystem. Earthworms, which have an indicative function for soil health and play a vital role in maintaining soil ecological functions, have not been fully studied in terms of their susceptibility to FSA. This study examined the effects of different concentrations of FSA on three ecotypes of earthworms (Eisenia fetida (epigeic), Metaphire guillelmi (anecic), and Aporrectodea caliginosa (endogeic)) and found varying trade-off strategy of their growth and reproduction. When subjected to FSA stress, E. fetida prioritized reproduction, A. caliginosa prioritized growth, while M. guillelmi maintained consistent growth and reproduction, effectively allocating the acquired biomass to reproduction. The study also analyzed the oxidative stress response, gene expression, and an integrated biomarker response. The strongest induction performance of the three ecotypes of earthworms was in the expression of antioxidant enzymes such as CAT, POD, SOD, and P450 expression, while the performance was significantly different in AChE activity, AChE and HSP70 expression, which may lead to differences in toxicity and detoxification mechanisms of earthworms in different ecotypes. The partial least squares-path model (PLS-PM) also showed that the three ecotypes of earthworms exhibited different toxicity, detoxification and regulatory pathways under FSA stress. M. guillelmi had the highest IBRv2 index (28.67-42.90). At the same time, the FSA bioaccumulation tended to be stable with increasing concentration, and its main detoxification ability (GST activity and P450 expression) could still maintain the same level as CK at high concentrations, indicating that it is very likely to be a potential earthworm type for FSA remediation. This study firstly provides a comprehensive assessment of FSA's toxic effects on different ecotypes of earthworms and highlights the importance of identifying potential resistant species for soil remediation.

Nickel oxide nanoparticles decrease the accumulation of atrazine in earthworms

Nickel oxide nanoparticles (NiO-NPs) are common nanomaterials that may be released into the environment, affecting the toxicity of other contaminants. Atrazine (ATZ) is a commonly used herbicide that can harm organisms due to its persistence and bioaccumulation in the environment. Although the toxicity of ATZ to earthworms is well-documented, the risk of co-exposure with NiO-NPs increases as more nanoparticles accumulate in the soil. In this study, we investigated the effects and mechanisms of NiO-NPs on the accumulation of ATZ in earthworms. The results showed that after day 21, the antioxidant system of the cells under ATZ treatment alone was adversely affected, with ROS content 36.05 % higher than that of the control (CK) group. However, the addition of NiO-NPs reduced the ROS contents in the earthworms by 0.6 %- 32.3 %. Moreover, analysis of earthworm intestinal sections indicates that NiO-NPs mitigated cellular and tissue damage caused by ATZ. High-throughput sequencing revealed that NiO-NPs in earthworm intestines increased the abundance of Pseudomonas aeruginosa and Aeromonas aeruginosa. Additionally, the enhanced function of the ABC transport system in the gut resulted in lower accumulation of ATZ in earthworms. In summary, NiO-NPs can reduce the accumulation and thus the toxicity of ATZ in earthworms. Our study contributes to a deeper understanding of the effects of NiO-NPs on co-existing pollutants.

Combined toxic effects of fluxapyroxad and multi-walled carbon nanotubes in Xenopus laevis larvae

Carbon nanomaterials rarely exist in isolation in the natural environment, and their combined effects cannot be ignored. Multi-walled carbon nanotubes (MWCNTs) have shown tremendous potential applications in diverse fields, including pollution remediation, biomedicine, energy, and smart agriculture. However, the combined toxicities of MWCNTs and pesticides on non-target organisms, particularly amphibians, are often overlooked. Fluxapyroxad (FLX), a significant succinate dehydrogenase inhibitor fungicide, has been extensively utilized for the protection of food and cash crops and control of fungi. This raises the possibility of coexistence of MWCNTs and FLX. The objective of this study was to explore the individual and combined toxic effects of FLX and MWCNTs on the early life stages of Xenopus laevis. Embryos were exposed to varying concentrations of FLX (0, 5, and 50 μg/L) either alone or in combination with MWCNTs (100 μg/L) for a duration of 17 days. The findings indicated that co-exposure to FLX and MWCNTs worsened the inhibition of growth, liver damage, and dysregulation of enzymatic activity in tadpoles. Liver transcriptomic analysis further revealed that the presence of MWCNTs exacerbated the disturbances in glucose and lipid metabolism caused by FLX. Additionally, the combined exposure groups exhibited amplified alterations in the composition and function of the gut microflora. Our study suggests that it is imperative to pay greater attention to the agricultural applications, management and ecological risks of MWCNTs in the future, considering MWCNTs may significantly enhance the toxicity of FLX.

Co-exposure of butyl benzyl phthalate and TiO2 nanomaterials (anatase) in Metaphire guillelmi: Gut health implications by transcriptomics

During the COVID-19 pandemic, an abundance of plastic face masks has been consumed and disposed of in the environment. In addition, substantial amounts of plastic mulch film have been used in intensive agriculture with low recovery. Butyl benzyl phthalate (BBP) and TiO2 nanomaterials (nTiO2) are widely applied in plastic products, leading to the inevitable release of BBP and nTiO2 into the soil system. However, the impact of co-exposure of BBP and nTiO2 at low concentrations on earthworms remains understudied. In the present study, transcriptomics was applied to reveal the effects of individual BBP and nTiO2 exposures at a concentration of 1 mg kg-1, along with the combined exposure of BBP and nTiO2 (1 mg kg-1 BBP + 1 mg kg-1 nTiO2 (anatase)) on Metaphire guillelmi. The result showed that BBP and nTiO2 exposures have the potential to induce neurodegeneration through glutamate accumulation, tau protein, and oxidative stress in the endoplasmic reticulum and mitochondria, as well as metabolism dysfunction. The present study contributes to our understanding of the toxic mechanisms of emerging contaminants at environmentally relevant levels and prompts consideration of the management of BBP and nTiO2 within the soil ecosystems.

Toxicity of carbon nanofibers in earthworms (Lumbricus terrestris) naturally infected with Monocystis sp

Although the ecotoxicity of carbon-based nanomaterials (CBNs) is known, the potential effect of carbon nanofibers (CNFs) on edaphic organisms has been insufficiently explored. Thus, we aimed at the ecotoxicity of CNFs (at 10 and 100 mg/kg) in Lumbricus terrestris earthworms naturally infected with Monocystis sp. After 28 days of exposure, treatments did not affect the survival rate. However, we observed a significant loss of body biomass, and Monocystis sp. infection in seminal vesicles was potentiated by exposure to CNFs. Earthworms exposed to CNFs showed a redox imbalance in the seminal vesicle, muscle, and intestine and an alteration in nitric oxide production in these organs. In muscles, we also noticed a significant reduction in AChE activity in earthworms exposed to CNFs. The histopathological analyses revealed the treatments' significant effect on the structures of the different evaluated tissues. Although we did not notice a concentration-response for several of the biomarkers, when taken together and after the application of Integrated Biomarker Response (IBR) and principal component analysis (PCA), we noticed that the response of earthworms to CNFs at 100 mg/kg showed a more significant deviation from the unexposed group. This was mainly determined by inhibiting antioxidant activity in the seminal vesicle, biochemical biomarkers assessed in muscle and intestine, and histomorphometric muscle biomarkers from earthworms exposed to CNFs at 100 mg/kg. Thus, we demonstrate that CNFs increase the parasite load of Monocystis sp. of adult L. terrestris earthworms and induce biochemical and histopathological changes, especially at 100 mg/kg. Our results point to the additional impact these nanomaterials can have on the health of earthworms, signaling the need for greater attention to their disposal and ecotoxicological effects on soil organisms.

Quantitative proteomic analysis of the mechanism of Cd toxicity in Enterobacter sp. FM-1: Comparison of different growth stages

Enterobacter sp. are widely used in bioremediation, but the mechanism of Cadmium (Cd) toxicity in Enterobacter sp. has been poorly studied. In the present study, we determined the tolerance of Enterobacter sp. FM-1 to Cd by analyzing the physiological and biochemical responses of FM-1 induced under Cd stress. Differentially expressed proteins (DEPs) under exposure to different Cd environments were analyzed by 4D-label-free proteomics to provide a comprehensive understanding of Cd toxicity in FM-1. The greatest total number of DEPs, 1148, was found in the High concentration vs. Control comparison group at 10 h. When protein expression was compared after different incubation times, FM-1 showed the highest Cd tolerance at 48 h. Additionally, with an increasing incubation time, different comparison groups gradually began to show similar growth patterns, which was reflected in the GO enrichment analysis. Notably, only 815 proteins were identified in the High concentration vs. Control group, and KEGG enrichment analysis revealed that these proteins were significantly enriched in the pyruvate metabolism, oxidative phosphorylation, peroxisome, glyoxylate and dicarboxylate metabolism, and citrate cycle pathways. These results suggested that an increased incubation time allows FM-1 adapt and survive in an environment with Cd toxicity, and protein expression significantly increased in response to oxidative stress in a Cd-contaminated environment during the pre-growth period. This study provides new perspectives on bacterial participation in bioremediation and expands our understanding of the mechanism of bacterial resistance under Cd exposure.

The effects of polyethylene microplastics on the growth, reproduction, metabolic enzymes, and metabolomics of earthworms Eisenia fetida

The existing data regarding the effects of polyethylene (PE) microplastics (MPs) smaller than 5 mm in size on earthworms are insufficient to fully comprehend their toxicity. In this study, earthworms Eisenia fetida were exposed to artificially added PE at a concentration ranging from 0.05 to 20 g/kg soil (0.005%-2%) for 60 days to determine the concentration range causing negative effects on earthworms and to uncover the potential toxic mechanisms. The individual growth, reproduction, and metabolic enzyme activities, including phase I enzymes (cytochrome P450 [CYP] 1A2, 2B6, 2C9, and 3A4), and phase II metabolic enzymes (superoxide dismutase (SOD), catalase (CAT), and glutathione sulfotransferase (GST)), and metabolomics were measured. The observed variations in responses of multiple cross-scale endpoints indicated that individual indices are less responsive to PE MPs than metabolic enzymes or metabolomics. Despite the absence of significant alterations in growth inhibition based on body weight, PE MPs at concentrations equal to or exceeding 2.5 g/kg were found to exert a toxic effect on earthworms, which was evidenced by significant changes in metabolic enzyme activities (CYP1A2, 2B6, 2C9, and 3A4, SOD, CAT, and GST) and important small molecule metabolites screened based on metabolomics, likely due to the bioaccumulation of PE. The toxicity of PE MPs to earthworms is inferred to be associated with neurotoxicity, oxidative damage, decreased detoxification capacity, energy metabolism imbalance, and impaired amino acid and purine metabolism due to bioaccumulation. The findings of this study will enhance our understanding of the molecular toxicity mechanisms of PE MPs and contribute to a more accurate assessment of the ecological risks posed by PE MPs in soil.

Nano-based smart formulations: A potential solution to the hazardous effects of pesticide on the environment

Inefficient usage, overdose, and post-application losses of conventional pesticides have resulted in severe ecological and environmental issues, such as pesticide resistance, environmental contamination, and soil degradation. Advances in nano-based smart formulations are promising novel methods to decrease the hazardous impacts of pesticide on the environment. In light of the lack of a systematic and critical summary of these aspects, this work has been structured to critically assess the roles and specific mechanisms of smart nanoformulations (NFs) in mitigating the adverse impacts of pesticide on the environment, along with an evaluation of their final environmental fate, safety, and application prospects. Our study provides a novel perspective for a better understanding of the potential functions of smart NFs in reducing environmental pollution. Additionally, this study offers meaningful information for the safe and effective use of these nanoproducts in field applications in the near future.

Reproductive damage and compensation of wild earthworm Metaphire californica from contaminated fields with long-term heavy metal exposure

Reproduction is a significant biological process for organisms responding to environmental stresses, however, little is known about the reproductive strategies of invertebrates under long-term exposure to contaminations. In this study, earthworm Metaphire californica (Kinberg, 1867) from contaminated fields with an increased metal gradient were collected to investigate their reproductive responses. The results showed heavy metals (Cd, Cu, Zn, and Pb) induced histological damage to earthworms' seminal vesicles, including tissue disorders and cavities, and decreases in mature spermatozoa. Sperm morphology analysis indicated deformity rates were up to13.2% (e.g. head swollen or missing) for worms from the most contaminated site, which coincided with DNA damages. Furthermore, the computer-assisted sperm analysis (CASA) system was employed for the evaluation of sperm kinetic traits. Results suggested earthworms exposed to higher contamination showed a lower sperm viability rate but faster sperm velocity after re-exposure with Cd solution (like the curvilinear velocity and straight-line velocity paraments) compared with those from relatively clean sites. The activities of lactate dehydrogenase and sorbitol dehydrogenase showed the highest 32.5% and 12.5% up-regulation respectively with the increased metal gradient. In conclusion, this study elucidated the earthworm reproductive toxicity, underlying reproductive compensation, metal stress-induced damages, and adaptive responses caused by heavy metal exposure, while also providing the possibility of sperm trait analysis (CASA) for related earthworm toxicological studies.