Exposure to lethal levels of benzo[a]pyrene or cadmium trigger distinct protein expression patterns in earthworms (Eisenia fetida)

Metaphire guillelmi exhibited predominant capacity of arsenic efflux

Earthworm could regulate their body concentration of arsenic via storage or excretion, and the ability of As efflux among different earthworms is not consistent. Here, whole and semi As exposure patterns with 0-10-30-60-100 mg kg-1 exposure concentrations were set to characterize the As efflux in geophagous earthworm, Metaphire guillelmi. Cast As (As-C) and earthworms' antioxidative responses were monitored to explore the efflux mechanisms under 30 mg kg-1 As-spiked soil (As30), besides, As concentration in earthworm tissue after egestion and dissection depurations were compared. In the whole exposure pattern, As concentration in gut content (As-G, 19.2-120.3 mg kg-1) surpassed that in the tissue (As-T, 17.2-53.2 mg kg-1), and they both increased with exposure concentrations. With the prolong time, they firstly increased and kept stable between day 10-15, then As-G increased while As-T decreased between day 15-20. In the semi-exposure pattern, both As-G and As-T decreased when M. guillelmi was transferred to clean soil for 5 days. During the 42-day incubation in As30, the antioxidative responses including reactive oxygen species (ROS), glutathione (GSH) and glutathione-S-transferase (GST) were firstly increased and then decreased, and As-C (13.9-43.9 mg kg-1) kept higher than As-G (14.2-35.1 mg kg-1). Significantly positive correlations were found between As-T and GSH, As-C and GST. Moreover, tissue As after dissection (11.6-22.9 mg kg-1) was obviously lower than that after egestion (11.4-26.4 mg kg-1), but significantly related to ROS and GSH. Taken together, M. guillelmi exhibited excellent capacity of As efflux, and GSH explained tissue As accumulation while GST facilitated the As elimination via cast. Besides, dissection instead of egestion revealed the As efflux in M. guillelmi more accurately. These findings contributed to a better understanding of how geophagous earthworm M. guillelmi regulated tissue As accumulation for As stress tolerance, and recommended an optimal depuration mode to characterize As accumulation.

Toxicity of leachate from smoked cigarette butts to terrestrial animals: A case study on the earthworm Eisenia fetida

Cigarette butts, as easily overlooked littered wastes, have been evaluated for toxicity in various researches. In this study, we investigated the toxic effects of smoked cigarette butt leachate (SCBL) on the earthworm Eisenia fetida. The results showed the following: 1) E. fetida avoided SCBL in artificial soil, and the avoidance rate was positively correlated with the concentration of SCBL but negatively correlated with the exposure time; 2) the LD50 of SCBL on earthworms at 36 and 48 h of exposure were 3.71 × 10-4 and 2.67 × 10-4 butts/cm2, respectively. Moreover, both the body surface and intestinal tissues of E. fetida were damaged after exposure to SCBL; 3) the survival rates of E. fetida exposed to artificial soil with an SCBL of 3.6 butts/kg for 7 and 14 days were 80.00 ± 7.07 % and 68.00 ± 4.47 %, respectively; and 4) the mean biomass of the surviving E. fetida in all treated groups decreased with increasing SCBL concentration and exposure time. We concluded that SCBL exerted significant negative effects on soil animals, and suggested that SCBs should be collected, detoxified, and reused before entering the natural environment.

Silicon-based nanoparticles for mitigating the effect of potentially toxic elements and plant stress in agroecosystems: A sustainable pathway towards food security

Due to their size, flexibility, biocompatibility, large surface area, and variable functionality nanoparticles have enormous industrial, agricultural, pharmaceutical and biotechnological applications. This has led to their widespread use in various fields. The advancement of knowledge in this field of research has altered our way of life from medicine to agriculture. One of the rungs of this revolution, which has somewhat reduced the harmful consequences, is nanotechnology. A helpful ingredient for plants, silicon (Si), is well-known for its preventive properties under adverse environmental conditions. Several studies have shown how biogenic silica helps plants recover from biotic and abiotic stressors. The majority of research have demonstrated the benefits of silicon-based nanoparticles (Si-NPs) for plant growth and development, particularly under stressful environments. In order to minimize the release of brine, heavy metals, and radioactive chemicals into water, remove metals, non-metals, and radioactive components, and purify water, silica has also been used in environmental remediation. Potentially toxic elements (PTEs) have become a huge threat to food security through their negative impact on agroecosystem. Si-NPs have the potentials to remove PTEs from agroecosystem and promote food security via the promotion of plant growth and development. In this review, we have outlined the various sources and ecotoxicological consequences of PTEs in agroecosystems. The potentials of Si-NPs in mitigating PTEs were extensively discussed and other applications of Si-NPs in agriculture to foster food security were also highlighted.

The synergistic effect between biofertility properties and biological activities in vermicomposting: A comparable study of pig manure

Vermicomposting is a resource technology for managing animal excreta, whereas the internal relationships of the process are vital for its wide applications. The present study examined how macronutrient and micronutrient concentrations, microbial communities, and enzymatic activity of pig manure (PM) changed during the composting and vermicomposting processes and their internal interactions. The vermicomposting process increased macronutrients more significantly than composting (32.40% of total available nitrogen, 21.70% of total available phosphorous, and 12.70% of total available potassium). The vermicomposting reduced total organic carbon (7.91%), C/N ratio (61.35%), and humification index (56.47%) more than composting due to the quick decomposition of PM. After continual fertility optimization, the total microbial population, with the exception of total fungi, rose significantly to accelerate organics mineralization and improve macronutrients in vermicomposting compared to composting. Moreover, earthworm addition favored the stabilization of the PM containing higher concentrations of micronutrients after being catalyzed by the enhanced catalase activity and reduced sucrase activity after 90 days of vermicomposting. Principal component analysis and chord plots found that the generated vermicomposting products had higher fertility properties and biological activities induced by the synergistic effect of microorganisms and earthworms. These findings highlight vermicomposting is an eco-friendly management technology for processing PM and can be scaled up for agricultural applications.

Cytotoxicity profiling of decabromodiphenyl ethane to earthworm (Eisenia fetida): Abnormity-recovery-dysregulation physiological pattern reflects the coping mechanism

Response of terrestrial invertebrates to decabromodiphenyl ethane (DBDPE) is an emerging field of research nowadays, while cytotoxicity of DBDPE and self-defense strategies of invertebrates are poorly understood. In this study, earthworms (Eisenia fetida) were incubated in the DBDPE-spiked soil system (10, 30, 50, 70, and 100 mg kg^-1 dw) for 28-d uptake. The bioaccumulation and distribution of DBDPE, a series of biomarkers associated with lysosomes/mitochondria, and the apoptosis rate of coelomocytes have been evaluated on the 7th, 14th, 21th, and 28th day. At experimental endpoint, the autophagy/apoptosis phenomena have been observed under transmission electron microscopy and the expression levels of six target genes have been explored. Findings in this paper revealed that: bioaccumulation factors decreased with the incremental DBDPE concentrations in the soil. Intestinal ingestion, but not epidermal contact predominated the absorption of DBDPE. The fluctuations of biomarkers and the apoptosis rate were described as the "abnormity-recovery-dysregulation" pattern. Intense oxidative stress, energy demands, membrane-system damage, pathological organelles, and apoptosis were observed in the treated groups. Conclusively, the cytotoxicity of DBDPE initiated the mitochondrial apoptosis pathway which affected the physiological status of lysosomes, autophagy, and the expression of genes. The coping mechanisms of Eisenia fetida to DBDPE included activating mitochondrial electron transport processes, reorganizing actin cytoskeleton, and initiating autophagy. Earthworms resisted the cytotoxicity of DBDPE to a certain extent, while long-term exposure still resulted in apoptosis of coelomocytes. This study works as a laboratory simulation for the environmental safety evaluation of DBDPE and the detoxification mechanisms for earthworm.

Sensitivity of midgut physiological parameters of Lymantria dispar L. larvae to benzo[a]pyrene in populations with different multigeneration contact to environmental pollutants

Accumulation of organic pollutants in the environment calls for sensing physiological parameters adequate to indicate the presence of contaminants and their effects on ecosystems. Evidence points to the importance of insect adaptations in their habitats for the assessment of sensitive biomarkers so we examined the influence of origin and multigenerational adaptations of the Lymantria dispar larvae to chronic benzo[a]pyrene (B[a]P) treatment under laboratory conditions. The main aim was to compare reactions of larvae from unpolluted and polluted forests using alkaline phosphatase (ALP), acid phosphatase (ACP), and carboxylesterase (CE) specific activities in the midgut, including electrophoretic isoform patterns; midgut expression levels of Hsp70, larval development time (DT), and midgut mass (MM), after chronic exposure to 5 and 50 ng of B[a]P/g dry food weight. The biomarker potential of these parameters regarding larval pre-exposure history to pollution was estimated by principal component analysis (PCA). B[a]P treatment resulted in inhibition of ALP activity, a rise of CE activity, and reduction of MM in larvae from the unpolluted forest, while the population from the polluted forest showed significant elevation of Hsp70 expression in the midgut, prolonged DT, and reduction of MM. PCA confirmed variations in responses of the selected parameters regarding population origin. The obtained results provide insight into insect population variability concerning physiological responses to pollutants. It is indicative that all investigated physiological parameters of L. dispar larvae showed origin-dependent responses to long-term presence of B[a]P, which may be of great importance in ecotoxicological research.

Exposure to benzo[a]pyrene triggers distinct patterns of microRNA transcriptional profiles in aquatic firefly Aquatica wuhana (Coleoptera: Lampyridae)

Larval aquatic fireflies in fresh water are adversely affected by water pollutants such as benzo(a)pyrene (BaP). However, their response to BaP stress at the microRNA (miRNA)-regulatory level remains unknown. Here, transcriptomes containing 31,872 genes and six miRNA transcriptional profiles were obtained for Aquatica wuhana larvae, and comparative analysis was performed between larvae exposed to BaP (0.01 mg/L) and unexposed controls. Fifteen of 114 miRNAs identified via bioinformatics were detected as differentially expressed (DEMs) upon BaP exposure. Analysis results of predicted target genes of DEM suggests that BaP exposure primarily triggered transcriptional changes of miRNA associated with five major regulatory categories: 1) osmotic balance, 2) energy metabolic efficiency, 3) development, 4) xenobiotic metabolism (oxidative stress), and 5) innate immune response. Based on six innate immune- and xenobiotic metabolism-related pathways enriched by the predicted DEM targets, 11 key BaP-responsive DEMs were further screened to investigate dynamic changes of expression in response to BaP stress at five time points, and also to validate the miRNA sequencing data using quantitative real-time PCR. This study provides valuable information for the protection of firefly resources and supplements the understanding of miRNA regulatory mechanisms in response to water deterioration.

World within world: Intestinal bacteria combining physiological parameters to investigate the response of Metaphire guillelmi to tetracycline stress

Due to the abusive usage of antibiotics in animal husbandry, a large amount of residual antibiotics has been released into the environment, therein posing great threat against both environment security and public health. Therefore, it is of great significance to investigate the toxicity of antibiotics on the widely-applied bioindicator-earthworm. In this work, the physiological parameters and the intestinal bacteria community of Metaphire guillelmi were monitored simultaneously to evaluate their sensitivity to the tetracycline (TC) exposure. As expected, the antioxidant enzyme activity and coelomocyte apoptosis acted fairly well as biomarkers for the TC toxicity. In contrast, the intestinal bacteria of Metaphire guillelmi responded varyingly to different TC doses. When TC concentration increased from 0 to 35.7 μg cm^-2, the percentage of the Proteobacteria phylum declined significantly from 85.5% to 34.4%, while the proportions of the Firmicutes, Planctomycetes and Atinomycete phyla clearly increased (p < 0.05). Meanwhile, the levels of TC resistance genes tetA, tetC, and tetW increased with the increasing TC concentration, in contrast to the declined abundance in denitrifying genes nirS and nosZ (p < 0.05). By analyzing the correlation between the antioxidant enzyme activity and the dominant intestinal bacteria in the worm gut, it is interesting to found that the four dominant bacteria genera Mesorhizobium, Aliihoeflea, Romboutsia, and Nitrospira are the promising bioindicator of TC stress due to their sensitive response. This work shed novel light on evaluating the ecotoxicological risks posed by residual TC in environment by using a combination of physiological parameters and intestinal bacterial activity in earthworms.

Enhanced photocatalytic disinfection of Escherichia coli K-12 by porous g-C3N4 nanosheets: Combined effect of photo-generated and intracellular ROSs

The porous graphitic carbon nitride nanosheets (PCNSs) with high yields were synthesized by using one-step chemical exfoliation method. PCNSs accelerated separation efficiency of photo-generated electron-hole pairs in comparison to bulk graphitic carbon nitride. The PCNS5 (exfoliation for 5 h) exhibited optimal photocatalytic disinfection capability towards Escherichia coli K-12 under simulated solar light irradiation with complete disinfection of 6.5 log₁₀ cfu/mL of E. coil K-12 within 2 h. The enhanced photocatalytic activity of PCNS5 originated from mesoporous nanosheet structure. The possible mechanism of photocatalytic disinfection has proposed that intracellular reactive oxygen species levels and the activities of antioxidant enzymes (e.g., catalase and superoxide dismutase) were enhanced. Transmission electron microscope images observed during photocatalytic disinfection process suggested that the cell membrane was regarded as the first target for oxidation, resulting in a faster leakage of cytoplasmic content and finally degradation of DNA leading to bacterial death. Furthermore, the trapping experiment showed that superoxide radical (•O₂^-) and holes (h⁺) were responsible for E. coli K-12 disinfection by PCNS5.

Metabolic and proteomic mechanism of benzo[a]pyrene degradation by Brevibacillus brevis

Benzo[a]pyrene (BaP) is a model compound of polycyclic aromatic hydrocarbons. The relationship between its toxicity and some target biomolecules has been investigated. To reveal the interactions of BaP biodegradation and metabolic network, BaP intermediates, proteome, carbon metabolism and ion transport were analyzed. The results show that 76% BaP was degraded by Brevibacillus brevis within 7 d through the cleavage of aromatic rings with the production of 1-naphthol and 2-naphthol. During this process, the expression of xylose isomerase was induced for xylose metabolism, whereas, α-cyclodextrin could no longer be metabolized. Lactic acid, acetic acid and oxalic acid at 0.1-1.2 mg dm^-3 were released stemming from their enhanced biosynthesis in the pathways of pyruvate metabolism and citrate cycle, while 5-7 mg dm^-3 of PO₄^3- were transported for energy metabolism. The relative abundance of 43 proteins was significantly increased for pyruvate metabolism, citrate cycle, amino acid metabolism, purine metabolism, ribosome metabolism and protein synthesis.

Comparative transcriptomic analysis provides insights into the response to the benzo(a)pyrene stress in aquatic firefly (Luciola leii)

Many studies have reported that behavior and bioluminescence of fireflies could be affected by changes in environment conditions. However, little is known about how the deterioration of the aquatic environment affects aquatic fireflies, particularly with respect to molecular responses following exposure to water pollutants, such as benzo(a)pyrene (BaP), which is a key indicator in environmental risk assessment because of the hazards it poses. Here, whole transcriptome sequencing and gene expression analysis were performed on freshwater fireflies (Luciola leii) exposed to BaP (concentration of 0.01 mg/L). Four transcriptomic libraries were constructed for the control and treatment groups, including two biological replicates. From the mixed pools (each pool contains 60 individuals from three time points), a total of 54,282 unigenes were assembled. Furthermore, 329,337 of Single-nucleotide Polymorphisms (SNPs) and 1324 of Simple Sequence Repeats (SSRs) were predicted using bioinformatics, which is useful for the future development of molecular markers. Subsequently, 2414 differently expressed genes (DEGs) were identified in response to BaP stress in comparison to the control, including 1350 up-regulated and 1064 down-regulated DEGs. Functional enrichment showed that these DEGs are primarily related to innate immunity; xenobiotic biodegradation and response, biomacromolecule metabolism, biosynthesis, and absorption. Eight key BaP-responsive DEGs were screened to survey the dynamic changes of expression in response to BaP stress at different time points, and to validate the RNA sequencing data using quantitative real-time PCR. The results indicate that the expression of genes encoding UGT, CYP3A, CYP9, CYP6AS5 and ADHP were induced, while those encoding UGT2B10L, PTGDS, and ALDH were reduced, to participate in response to the BaP exposure and potentially help counteract the adverse effects of BaP. This investigation provides insight into the toxicological response of fireflies to the occurrence of water deterioration.

Assessment of the toxicity of silicon nanooxide in relation to various components of the agroecosystem under the conditions of the model experiment

Investigation of SiO₂ nanoparticles (NPs) effect on Eisenia fetida showed no toxic effect of the metal at a concentration of 250, 500 and 1000 mg per kg of soil, but conversely, a biomass increase from 23.5 to 29.5% (at the protein level decrease from 60 to 80%). The reaction of the earthworm organism fermentative system was expressed in the decrease in the level of superoxide dismutase (SOD) on the 14th day and in the increase in its activity to 27% on the 28th day. The catalase level (CAT) showed low activity at average element concentrations and increase by 39.4% at a dose of 1000 mg/kg. Depression of malonic dialdehyde (MDA) was established at average concentrations of 11.2% and level increase up to 9.1% at a dose of 1000 mg/kg with the prolongation of the effect up to 87.5% after 28-day exposure. The change in the microbiocenosis of the earthworm intestine was manifested by a decrease in the number of ammonifiers (by 42.01-78.9%), as well as in the number of amylolytic microorganisms (by 31.7-65.8%). When the dose of SiO₂ NPs increased from 100 to 1000 mg/kg, the number of Azotobacter increased (by 8.2-22.2%), while the number of cellulose-destroying microorganisms decreased to 71.4% at a maximum dose of 1000 mg/kg. The effect of SiO₂ NPs on Triticum aestivum L. was noted in the form of a slight suppression of seed germination (no more than 25%), an increase in the length of roots and aerial organs which generally resulted in an increase in plant biomass. Assessing the soil microorganisms' complex during introduction of metal into the germination medium of Triticum aestivum L., there was noted a decrease in the ammonifiers number (by 4.7-67.6%) with a maximum value at a dose of 1000 mg/kg. The number of microorganisms using mineral nitrogen decreased by 29.5-69.5% with a simultaneous increase in the number at a dose of 50 mg/kg (+ 20%). Depending on NP dose, there was an inhibition of the microscopic fungi development by 18.1-72.7% and an increase in the number of cellulose-destroying microorganisms. For all variants of the experiment, the activity of soil enzymes of the hydrolase and oxidoreductase classes was decreased.

Benzo(a)pyrene degradation by cytochrome P450 hydroxylase and the functional metabolism network of Bacillus thuringiensis

The relationship between benzo(a)pyrene biodegradation and certain target biomolecules has been investigated. To regulate the degradation process, the associated metabolism network must be clarified. To this end, benzo(a)pyrene degradation, carbon substrate metabolism and exometabolomic mechanism of Bacillus thuringiensis were analyzed. Benzo(a)pyrene was degraded through hydroxylation catalyzed by cytochrome P450 hydroxylase. After the treatment of 0.5 mg L^-1 of benzo(a)pyrene by 0.2 g L^-1 of cells for 9 d, biosorption and degradation efficiencies were measured at approximately 90% and 80%, respectively. During this process, phospholipid synthesis, glycogen, asparagine, arginine, itaconate and xylose metabolism were significantly downregulated, while glycolysis, pentose phosphate pathway, citrate cycle, amino sugar and nucleotide sugar metabolism were significantly upregulated. These findings offer insight into the biotransformation regulation of polycyclic aromatic hydrocarbons.

Benzo(a)pyrene inhibits the accumulation and toxicity of cadmium in subcellular fractions of Eisenia fetida

Cadmium (Cd) and benzo [a]pyrene (BaP) often co-occur in the environment, and the critical body residue of organisms is used as an indicator of the toxic effects of contaminants. However, little is known about their distributions and toxicities when pollution of Cd and BaP are combined. Semi-static solution culture experiment was used to study the impacts of BaP on the subcellular distribution of the toxic metal Cd in the earthworm Eisenia fetida. We explored the mechanisms by which this organism responds to combined exposure to these pollutants by measuring the protein content of each of three subcellular fractions, as well as acetylcholinesterase (AChE) and glutathione S-transferase (GST) activities. The subcellular partitioning of Cd was heterogeneous and Cd mainly accumulated in the cytosolic fraction (Fraction C), which was previously reported to be involved in metal immobilization. In Fraction C, Cd accumulation was correlated with the external concentration to which the earthworm had been exposed; however, in the presence of BaP, Cd accumulation was inhibited and plateaued at high external Cd concentrations. A principal component analysis revealed that this decreased Cd accumulation might be caused by increases in GST activity, which likely increased the excretion of Cd. BaP was also found to stimulate protein biosynthesis and upregulate AChE and GST activities in the debris fraction (Fraction E), indicating other potential detoxification mechanisms in this fraction. Granule fraction (Fraction D) had a lower protein content, AChE and GST activities than the other subcellular fractions, supporting previous findings that Fraction D is largely inert.

Differential expression of proteins in the leaves and roots of cadmium-stressed Microsorum pteropus, a novel potential aquatic cadmium hyperaccumulator

Microsorum pteropus is a fully or partially submerged Polypodiaceae fern that has been proven to be a potential Cd aquatic hyperaccumulator. Proteomic analysis was used in this study to investigate the resistance mechanisms of M. pteropus root and leaf tissues under Cd stress. M. pteropus plants were exposed to up to 500 μM Cd in hydroponics for 7 days. The plant can accumulate >4,000 mg/kg Cd in both root and leaf dry mass. Meanwhile, the proteins in roots and leaves in the 500 μM Cd treatment were separated and analyzed by proteomics. Eight proteins with altered expression in roots and twenty proteins with altered expression in leaves were identified using MALDI-TOF/TOF-MS (matrix-assisted laser desorption/ionization time of flight mass spectrometry) in this study. The proteins were involved in energy metabolism, antioxidant activity, cellular metabolism and protein metabolism. However, just three proteins were significantly differentially expressed in both tissues, and they were all involved in basal metabolism, indicating different resistance mechanisms between roots and leaves. Root tissues of M. pteropus mainly resist Cd damage by antioxidants and the enhancement of energy metabolism, while leaf tissues of M. pteropus mainly protect themselves by maintaining photosynthetic functions and the regulation of cellular metabolism.

Chemical and biological assessment of Cd-polluted sediment for land use: The effect of stabilization using chitosan-coated zeolite

Disposal of dredged sediment contaminated with heavy metals on site or in landfills inevitably causes leaching of metals that generate new environmental problems. In this study, we investigated the effectiveness of stabilizing heavy metal Cd in sediment taken from Dongting Lake, China, using a chitosan-coated zeolite, and assessed the feasibility of reusing the stabilized sediment in river bank soil based on chemical and biological analyses. Results showed that the addition of chitosan-coated zeolite significantly reduced acid-exchangeable Cd by 8% in the dredged sediment and 7% in a sediment-soil mixture. Cadmium leachability was greatly reduced in the amended sediment or sediment-soil mixture. Toxicity bioassay using Eisenia fetida showed the mortality rate of worms reduced by 16% in sediment-soil mixture with a Cd concentration of 550 mg/kg and by 17% under a Cd concentration of 250 mg/kg, both with the addition of modified zeolite. Moreover, assimilation of Cd in the earthworms was decreased by a maximum of 36 mg/kg in the sediment-soil mixture with zeolite amendment. These results indicate that the reuse of Cd-contaminated sediment following chitosan-coated zeolite modification is a feasible option for treating the dredged sediment, and could thus benefit both aquatic and terrestrial systems.