Toxic effects of fragmented polyethylene terephthalate particles on the marine rotifer Brachionus koreanus: Based on ingestion and egestion assay, in vivo toxicity test, and multi-omics analysis

Microplastics (MPs) are a major concern in marine ecosystem because MPs are persistent and ubiquitous in oceans and are easily consumed by marine biota. Although many studies have reported the toxicity of MPs to marine biota, the toxicity of environmentally relevant types of MPs is little understood. We investigated the toxic effects of fragmented polyethylene terephthalate (PET) MP, one of the most abundant MPs in the ocean, on the marine rotifer Brachionus koreanus at the individual and molecular level. No significant rotifer mortality was observed after exposure to PET MPs for 24 and 48 h. The ingestion and egestion assays showed that rotifers readily ingested PET MPs in the absence of food but not when food was supplied; thus, there were also no chronic effects of PET MPs. In contrast, intracellular reactive oxygen species levels and glutathione S-transferase activity in rotifers were significantly increased by PET MPs. Transcriptomic and metabolomic analyses revealed that genes and metabolites related to energy metabolism and immune processes were significantly affected by PET MPs in a concentration-dependent manner. Although acute toxicity of PET MPs was not observed, PET MPs are potentially toxic to the antioxidant system, immune system, and energy metabolism in rotifers.

Machine learning-based water quality prediction using octennial in-situ Daphnia magna biological early warning system data

Biological early warning system (BEWS) has been globally used for surface water quality monitoring. Despite its extensive use, BEWS has exhibited limitations, including difficulties in biological interpretation and low alarm reproducibility. This study addressed these issues by applying machine learning (ML) models to eight years of in-situ BEWS data for Daphnia magna. Six ML models were adopted to predict contamination alarms from Daphnia behavioral parameters. The light gradient boosting machine model demonstrated the most significant improvement in predicting alarms from Daphnia behaviors. Compared with the traditional BEWS alarm index, the ML model enhanced the precision and recall by 29.50% and 43.41%, respectively. The speed distribution index and swimming speed were significant parameters for predicting water quality warnings. The nonlinear relationships between the monitored Daphnia behaviors and water physicochemical water quality parameters (i.e., flow rate, Chlorophyll-a concentration, water temperature, and conductivity) were identified by ML models for simulating Daphnia behavior based on the water contaminants. These findings suggest that ML models have the potential to establish a robust framework for advancing the predictive capabilities of BEWS, providing a promising avenue for real-time and accurate assessment of water quality. Thereby, it can contribute to more proactive and effective water quality management strategies.

Fungal Microbiome of Alive and Dead Korean Fir in its Native Habitats

A rapid decline of Abies koreana has been reported in most of the natural alpine habitats in Korea. It is generally accepted that this phenomenon is due to climate change even though no clear conclusions have been drawn. Most research has focused on abiotic environmental factors, but studies on the relationships between A. koreana and soil fungal microbiomes are scarce. In this study, the rhizoplane and rhizosphere fungal communities in the alive and dead Korean fir trees from its three major natural habitats including Mt. Deogyu, Mt. Halla, and Mt. Jiri in Korea were investigated to identify specific soil fungal groups closely associated with A. koreana. Soil fungal diversity in each study site was significantly different from another based on the beta diversity calculations. Heat tree analysis at the genus level showed that Clavulina, Beauveria, and Tomentella were most abundant in the healthy trees probably by forming ectomycorrhizae with Korean fir growth and controlling pests and diseases. However, Calocera, Dacrymyces, Gyoerffyella, Hydnotrya, Microdochium, Hyaloscypha, Mycosymbioces, and Podospora were abundant in the dead trees. Our findings suggested that Clavulina, Beauveria, and Tomentella are the major players that could be considered in future reforestation programs to establish ectomycorrhizal networks and promote growth. These genera may have played a significant role in the survival and growth of A. koreana in its natural habitats. In particular, the genus Gyoerffyella may account for the death of the seedlings. Our work presented exploratory research on the specific fungal taxa associated with the status of A. koreana.

Metabolomic analysis of combined exposure to microplastics and methylmercury in the brackish water flea Diaphanosoma celebensis

Owing to their widespread distribution and high bioaccumulation, microplastics (MPs) and mercury (Hg) are considered major threats to the ocean. MP interacts with Hg because of its high adsorption properties. However, their toxicological interactions with marine organisms, especially combined effects at the molecular level, are poorly understood. This study investigated the single and combined effects of MP and Hg on the metabolic profile of the brackish water flea Diaphanosoma celebensis. A total of 238 metabolites were significantly affected by MP, Hg, or MP + Hg. Metabolite perturbation patterns showed that toxicity of Hg and MP + Hg was similar and that of MP was not significant. Among the 223 metabolites affected by Hg, profiles of 32 unannotated metabolites were significantly different from those of MP + Hg, and combined effects of MP + Hg decreased the effect of Hg on 25 of these metabolites. Only 11 annotated metabolites were significantly affected by Hg or MP + Hg and were related to carbohydrate, lipid, vitamin, and ecdysteroid metabolism. Ten metabolites were decreased by Hg and MP + Hg and were not significantly different between the exposure groups. Enrichment analysis showed that galactose, starch, and sucrose metabolism were the most affected pathways. These findings suggest that MP has negligible toxic effect, and Hg can induce energy depletion, membrane damage, and disruption of growth, development, and reproduction. Although the impact of MP was negligible, the combined effects of MP + Hg could be metabolite specific. This study provides better understanding of the combined effects of MP and Hg on marine organisms.

Transcriptome and computational approaches highlighting the molecular regulation of Zacco platypus induced by mesocosm exposure to common disinfectant chlorine

Chlorine (Cl₂) is a disinfectant often used in swimming pools and water treatment facilities. However, it is released into aquatic ecosystems, where it may harm non-targeted organisms. Here, we performed a mesocosm experiment exposing Zacco platypus (Z. platypus) to biocide Cl₂ for 30 days (30 d) at two days' time points 15 days (15 d) and 30 d samples were collected. Here, Z. platypus was exposed to a sublethal concentration (0.1 mg/L) of Cl₂, and comparative transcriptomics analyses were performed to determine their response mechanisms at the molecular level. According to RNA sequencing of the whole-body transcriptome, 860 and 1189 differentially expressed genes (DEGs) were identified from the 15 d and 30 d responses to Cl₂, respectively. After enrichment analysis of GO (Gene Ontology) functions and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways, identified DEGs were demonstrated to be associated with a variety of functions, including "ion binding and transmembrane transporters". Cl₂ also induced oxidative stress in Z. platypus by increasing the levels of reactive oxygen species (ROS) while decreasing the catalase (CAT) content and the levels of solute carrier family 22 member 11 (slc22a11), Caspase-8 (casp-8), inducible nitric oxide synthase (NOS2), cytosolic phospholipase A2 gamma (PLA2G4). However, Z. platypus still allows recovery during stress suspension by increasing the expression levels of solute carrier family proteins. The GO and KEGG annotation results revealed that the expression of DEGs were related to the detoxification process, immune response, and antioxidant mechanism. Additionally, protein-protein interaction networks (PPI) and cytoHubba analyses identified sixteen hub genes and their interaction. These findings elucidate the regulation of various DEGs and signaling pathways in response to Cl₂ exposure, which will improve our knowledge and laid foundation for further investigation of the toxicity of Cl₂ to Z. platypus.

Application of jetventurimixer for developing low-energy-demand and highly efficient aeration process of wastewater treatment

In biological wastewater treatment, the oxygen supply in an aeration tank is the most important factor for removing organic pollutants, but it takes a large amount of electricity to generate the oxygen supply required. The Jetventurimixer (JVM) is a device that applies Bernoulli’s principle, and the difference in flow rate pressure through the impeller is generated by the rotational force. Due to this physical mechanism, this device can supply oxygen in the atmosphere to the bioreactor without additional power. In this study, the JVM-based aeration process was developed for more efficient water treatment that demands lower energy. Parameters were measured for validating the efficiency and lower power demands, including the oxygen mass transfer characteristics and power efficiency. The results indicated that all parameters related to the oxygen mass transfer characteristics were advanced in performance by more than 200 % compared to those of the conventional air diffuser. In the case of power efficiency, it was confirmed that performance was 153–176 % higher. Therefore, it was confirmed that the JVM provides high-efficiency and low-energy benefits to the aeration process and, based on these advantages, the developed system seems to require further studies and validation for application to the water treatment system.

Metabolomic analysis predicted changes in growth rate in Daphnia magna exposed to acetaminophen

As urbanization and the global population increases, pollutants associated with municipal wastewater such as pharmaceuticals are becoming more prevalent in aquatic environments. Acetaminophen (paracetamol) is a widely used drug worldwide and one of the most frequently detected pharmaceuticals in freshwater ecosystems. This study investigated the impact of acetaminophen on the metabolite profile of Daphnia magna at two life stages; and used these metabolomic findings to hypothesize a potential impact at a higher organismal level which was subsequently tested experimentally. Targeted polar metabolite analysis by liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to measure changes in the concentration of 51 metabolites in the neonate (> 24 h old) and adult (8 day-old) daphnids following a 48-h exposure to sub-lethal concentrations of acetaminophen. The impact of acetaminophen on the metabolic profile of neonates was widely different from adults. Also, acetaminophen exposure perturbed the abundance of nucleotides more extensively than other metabolites. The acute metabolomic experimental results led to the hypotheses that exposure to sub-lethal concentrations of acetaminophen upregulates protein synthesis in D. magna and subsequently increases growth during early life stages and has an opposite impact on adults. Accordingly, a 10 day growth rate experiment indicated that exposure to acetaminophen elevated biomass production in neonates but not in adults. These novel findings demonstrate that a targeted analysis and interpretation of the changes in the polar metabolic profile of organisms in response to environmental stressors could be used as a tool to predict changes at higher biological levels. As such, this study further emphasizes the incorporation of molecular-level platforms as critical and robust tools in environmental assessment frameworks and biomonitoring of aquatic ecosystems.

Antioxidant enzyme activity in Daphnia magna under microscopic observation and shed carapace length as an alternative growth endpoint

Daphnia magna is an important organism for exposure studies in ecotoxicology. Body length measurement of a daphnid is a useful endpoint that represents the adverse effects of exposed chemicals or conditions on growth. This study questioned whether stress on body length measurement conditions while maintaining Daphnia magna on a slide glass results in any impact to antioxidant enzyme activity or growth. At the same time, the shed carapace length was tested to see if it could predict body length and be used as an alternative endpoint. The measured catalase (CAT) activity decreased as the exposure time to the on-slide conditions increased from 30 s to 120 s, although glutathione-S-transferase (GST) activity was not affected. On the other hand, regression between body length and two parameters of shed carapace length showed R² values, 0.869 and 0.924. Growth measured for each molting for three weeks was not affected by the exposure to the on-slide conditions. Finally, this study confirmed potential oxidative stress based on the exposure time dependent CAT activity in Daphnia magna under microscopic observation. More importantly, the shed carapace length was validated to reflect body length and it implies applicability of the new parameters to sublethal effect measurement using Daphnia magna. This study suggests potential interference is possible with the traditional growth measurement method on antioxidant enzyme activity in Daphnia magna and proposes better experimental practices to avoid the interference.

Comparative Study of the Synergistic Effects of Blending Raw/Torrefied Biomass and Vietnamese Anthracite Using Co-pyrolysis

Biomass can be upgraded via torrefaction, and torrefied kenaf (TK) is a fuel that allows blending with coal at high ratios. In the present study, raw kenaf (Hibiscus cannabinus L.) (RK) was torrefied at 523 K for 30 min and then mixed with Vietnamese anthracite (NinhBinh, NB) before co-pyrolysis. Thermogravimetric (TG) analysis was used to evaluate the behavior of RK, TK, and blended RK/TK during co-pyrolysis at biomass blending ratios (BBRs) of 0, 25, 50, 75, and 100 wt %. The TG and derivative thermogravimetry curves of a mixture of NB and RK (NBRK) were similar to those of RK. The decomposition curves of a mixture of NB and TK (NBTK) depended on the mass fraction of TK. Based on weight loss differences between the experimental and calculated data for the fuel blends, no interaction between the RK and anthracite was observed for all BBRs, whereas anthracite involving 50 and 75% TK exhibited synergistic effects. The temperature range for synergy and degree of synergy for NB and TK depended on the heating rate and mass ratio of TK. Kinetic parameters were calculated using the Friedman-non-isothermal free kinetic method at heating rates of 10, 20, and 40 K/min. The results showed that the activation energy (E) values of the NBRK at conversion ratios of 0.2-0.5 were equal to those of the RK, whereas they were superior at NB decomposition ratios of 0.6-0.8. NBTK1-1 (BBR of 50%) showed E values higher than those of NB at some conversion ratios, thus demonstrating a negative impact of blending. Further, NBTK1-3 (BBR of 75%) and NBTK3-1 (BBR of 25%) exhibited E values between those of NB and TK. The present study suggests that a high TK mass fraction (75%) in the blend for co-pyrolysis is optimal for the activation energy and volatile matter yield.

Endocrine Disruptor Exposure Causes Infochemical Dysregulation and an Ecological Cascade from Zooplankton to Algae

Endocrine disruption is intimately linked to controlling the population of pollutant-exposed organisms through reproduction and development dysregulation. This study investigated how endocrine disruption in a predator organism could affect prey species biology through infochemical communication. Daphnia magna and Chlorella vulgaris were chosen as model prey and predator planktons, respectively, and fenoxycarb was used for disrupting the endocrine system of D. magna. Hormones as well as endo- and exometabolomes were extracted from daphnids and algal cells and their culture media and analyzed using liquid chromatography with tandem mass spectrometry. Biomolecular perturbations of D. magna under impaired offspring production and hormone dysregulation were observed. Differential biomolecular responses of the prey C. vulgaris, indicating changes in methylation and infochemical communication, were subsequently observed under the exposure to predator culture media, containing infochemicals released from the reproducibly normal and abnormal D. magna, as results of fenoxycarb exposure. The observed cross-species transfer of the endocrine disruption consequences, initiated from D. magna, and mediated through infochemical communication, demonstrates a novel discovery and emphasizes the broader ecological risk of endocrine disruptors beyond reproduction disruption in target organisms.

Reproduction stage specific dysregulation of Daphnia magna metabolites as an early indicator of reproductive endocrine disruption

Rapid biomolecular observation in model indicator organisms has been considered as a potential predictor of water pollution from chronic and trace toxicants. This study evaluated the use of Daphnia magna metabolomic measurements as indicators for exposure to reproductive endocrine disruptors by using the model juvenile hormone analogue fenoxycarb. Because D. magna reproduction controls metabolic regulation, the reproduction stage was also carefully considered in metabolic observations and data analysis to examine differences. Comparisons of metabolite abundance regulation between 1 and 12 days of fenoxycarb exposure were performed to investigate the predictability of the sub-chronic (12 days) adverse impacts on reproduction and metabolic regulation based on acute (1 day) metabolic observations. ANOVA-simultaneous component analysis (ASCA) detected reversed patterns in direction of time-course metabolite abundance regulation with fenoxycarb exposure. For example, decreases in the abundances of leucine, asparagine, methionine, and isoleucine which then changed to increases were observed with time during fenoxycarb exposures. The reversed regulation pattern was observed at the last reproduction stage (stage 3), exclusively. Pearson correlation analysis showed that correlations of pairwise metabolites were disrupted with fenoxycarb exposure. Similar to ASCA, data normalization based on the reproduction stage improved the detectability of significant correlations. The disruption on ambient metabolite regulation patterns and pairwise metabolite correlations was consistently observed with both 1 and 12 days of fenoxycarb exposures for sets of select metabolites. The observed regulatory disruptions to these specific metabolites suggest altered oogenesis as the affected metabolites and the specific reproduction stage are related to successful oogenesis. This study demonstrates that D. magna metabolic dysregulation is a predictor of water contamination by endocrine disrupting compounds. The high predictability of sub-chronic (12 days) endocrine disruption was confirmed based on acute (1 day) metabolic observations. Furthermore, integration of the reproduction cycle information in D. magna metabolomics was validated by observing a reproduction stage specific dysregulation in metabolite abundance regulation, which was not observable from the broader data analysis. Consequently, this study confirms the potential for establishing a quantitative relationship between water quality and indicator species metabolic observations. Additionally, it was found that constraining variables relevant to toxicity mechanisms of interest, such as the reproduction stage, is a key consideration for extraction of ecologically meaningful information in environmental metabolomics.

Time-dependent biomolecular responses and bioaccumulation of perfluorooctane sulfonate (PFOS) in Daphnia magna

Perfluorooctane sulfonate (PFOS) is a persistent pollutant which is potentially harmful and bioaccumulative to aquatic organisms. To evaluate the regulatory alteration of select metabolites with PFOS exposure at early and typical acute exposure periods in an aquatic indicator species Daphnia magna, the hourly abundance of the twenty-three metabolites was investigated over 24 h. To evaluate the bioaccumulation potential of PFOS at a sub-lethal concentration in D. magna, the daily accumulation into D. magna for 16 days was also evaluated. Twenty-three targeted metabolites were quantified over 1 to 4 h and 21 to 24 h of PFOS exposure using liquid chromatography tandem mass spectrometry (LC-MS/MS). Daphnid to water PFOS concentration ratios were monitored separately over different days and life stages at 0 to 76 h and 2 to 16 days of PFOS exposure. The observed metabolite abundance and bioaccumulation in the exposed groups was compared between sampling times. The results reveal that sub-lethal PFOS exposure at 2 mg/L and 20 mg/L alters regulation of arginine, tyrosine and adenosine monophosphate which are directly and indirectly related to energy status. The temporal metabolic responses observed for the early exposure period (4 h), but not for the typical acute exposure period (24 h), suggest the dysregulation potency of PFOS on metabolite regulation of D. magna and the importance of early time-course monitoring approaches. Sixteen days of bioaccumulation monitoring showed that PFOS is more bioaccumulative in younger D. magna. The observation of time-dependent bioaccumulation of PFOS in D. magna requires further studies to define its precise mechanism. Interestingly, the bioaccumulation potential of PFOS was found to be consistent between 72 h and 16 day exposure periods. No difference on the body burden to water concentration ratio during about one third of the life span time (16 days), compared to the 72 h exposure, suggests that the prolonged exposure did not increase the bioaccumulation of PFOS in D. magna. This study demonstrates that the Daphnia metabolites are rapidly responding to sub-lethal PFOS exposure and provides information on life stage and time-dependent bioaccumulation potential of PFOS. As such, metabolite regulation is a sensitive indicator to sub-lethal PFOS exposure and can be informative when combined with other measures of toxicity.

Daphnia magna metabolic profiling as a promising water quality parameter for the biological early warning system

The inclusion of omics data into water quality monitoring programs is being considered to help alleviate the growing threat to water resources and ecosystem services. Despite the increasing need, the biological early warning system (BEWS), the widely used real-time water quality monitoring system, does not currently incorporate omics information, despite that metabolomics is a highly sensitive indicator of organism health and stress. We examined Daphnia magna metabolomics, which is the analysis of small molecules in living D. magna, as a potential water quality parameter for incorporation in the BEWS. The concentrations of 24 metabolites were measured with changes in water quality and variation of metabolite abundances was compared within and between conditions. Age-dependent monitoring revealed that matured individuals older than 8 days are appropriate model organisms for monitoring based on their low metabolomic variation as compared to younger daphnids. Hourly monitoring of metabolic variability and regulation under ambient and starved conditions demonstrated the rapid and sensitive detection of nutritional changes. Moreover, the metabolomic dysregulation due to exposure to the pollutant propranolol was also observed. By integrating all the observations, we found that the D. magna metabolome is a sensitive and useful parameter for detecting water quality changes and how these alter the function of keystone organisms. As such, this metabolomics-based framework is applicable to BEWS and highlights the beneficial advantages of integrating biomolecular and apical endpoint observations for enhanced performance in biomonitoring programs.

Reproduction Stage Differentiates the Time-Course Regulation of Metabolites in Daphnia magna

Daphnia magna is a keystone indicator zooplankton used in environmental quality assessments. Comparative metabolomics, which contrasts small biomolecular regulations under different conditions, has emerged as a sensitive and informative investigation tool for the assessment of environmental stressors on D. magna. Baseline metabolomic variation is likely impacted by the asexual reproduction cycle of D. magna; however, the relationship between metabolite concentration regulation and reproduction cycle has not been investigated. This study investigated the time-course regulation of 51 metabolites during different reproduction stages to determine how the reproduction cycle controlled the metabolite profile of D. magna. Two-way analysis of variance (ANOVA) results reveal that most metabolites show significantly differentiated concentrations by individual or a combination of reproduction stages and sampling time. On the basis of the partial least-squares-discriminant analysis (PLS-DA) and ANOVA-simultaneous component analysis (ANOVA-SCA), stages 2 and 3 of reproduction show similarity in metabolite abundance regulation compared to stage 1. Metabolites were classified as being either dependent or independent of reproduction in the pairwise concentration correlation based on Pearson correlation coefficients. This study observed that the D. magna reproduction stage is an important consideration and potential variable and should be considered carefully when conducting metabolomic experiments using D. magna.

Comparative microbial communities in tidal flats sediment on Incheon, South Korea

Coastal ecosystems, play critical ecological roles of which tidal flats are a significant component of coastal wetlands, such as habitat and nutrient cycling in aquatic biology. Microbial communities in tidal flats are known to play vital roles of self-purification. And the microbial ecology of the sediment is easily affected by human activities and pollution. In this paper, we applied pyrosequencing technology to investigate microbial communities in three different tidal flats (Ganghwa Island, Ongnyeon land region and Yeongjong Island) on the Incheon, Korea peninsula. A total of 16,906 sequences were obtained. We used these sequences to identify the dominant phyla in the three tidal flats: Proteobacteria, Chloroflexi, Actinobacteria, and Bacteroidetes. The composition of the bacterial community of Ganghwa Island and the Ongnyeon region were more similar to each other than they were to the bacterial community of Yeongjong Island. Simpson's dominance index of Yeongjong Island was higher than that of the other regions, and the Shannon diversity index of this region was the lowest. Previous research of samples in these regions indicated that the three tidal flats had similar geochemical characteristics. However, their bacterial communities were rather distinct. This might be because the analysis of microbial communities and physiochemical analysis have different perspectives. Therefore, the pyrosequencing of a bacterial community with physiochemical analysis is recommended as an effective monitoring tool for the comprehensive management of tidal flats.

Effect of β-adrenergic receptor agents on cardiac structure and function and whole-body gene expression in Daphnia magna

Propranolol (PRO), a human β-AR (β-adrenergic receptor) antagonist, is considered to result in specific effects in a non-target species, D. magna, based on our previous studies. The present study investigated the effects of β-AR agents, including an antagonist and agonist using pharmacologically relevant endpoints as well as a more holistic gene expression approach to reveal the impacts and potential mode of actions (MOAs) in the model non-target species. Results show that the responses in cardiac endpoints and gene expression in D. magna are partially similar but distinguishable from the observations in different organisms. No effect was observed on heart size growth in PRO and isoprenaline (ISO) exposure. The contraction capacity of the heart was decreased in ISO exposure, and the heart rate was decreased in PRO exposure. Time-series exposures showed different magnitudes of effect on heart rate and gene expression dependent on the type of chemical exposure. Significant enrichment of gene families involved in protein metabolism and biotransformation was observed within the differentially expressed genes, and we also observed differential expression in juvenile hormone-inducible proteins in ISO and PRO exposure, which is suspected of having endocrine disruption potential. Taken together, deviation between the effects of PRO and ISO in D. magna and other organisms suggests dissimilarity in MOAs or attributes of target bio-molecules between species. Additionally, PRO and ISO may act as endocrine disruptors based on the gene expression observation. Results in the present study confirm that it is challenging to predict ecological impact of active pharmaceutical ingredients (APIs) based on the available data acquired through human-focused studies. Furthermore, the present study provided unique data and a case study on the impact of APIs in a non-target organism.

Profiling the decomposition products of perfluorooctane sulfonate (PFOS) irradiated using an electron beam

Perfluorooctane sulfonate (PFOS) has been found in wastewater treatment plants (WWTPs) and in surface water as a result of domestic uses of textiles, electronics, and surfactants. The detection of PFOS in the aqueous environment has been linked to hazardous biological effects including estrogenicity and genotoxicity. To provide an alternative to conventional processes, one of the radical-based advanced oxidation and reduction processes being tested for treatment of refractory compounds in water, involves the use of an electron beam. Therefore, the aims of this study were to investigate the degradation efficiency of PFOS (100mg/L) by electron beam, to evaluate the predicted toxicity of the radiolysis products using the ECOSAR model, and to identify the radiolytic products of PFOS. As a result of using the ECOSAR model, the toxicity levels of by-products after electron beam treatment were reduced by decreasing the carbon-chain number of PFOS. The molecular structures of the radiolytic products were elucidated using authentic standards via liquid chromatography and tandem mass spectrometry, and by the interpretation of MS² fragmentation patterns of each product using liquid chromatography with quadrupole time of-flight mass spectrometry (LC-QTOF-MS). In total, ten radiolytic products were confirmed by LC-MS/MS, HPLC, and IC data matching with commercial standards. The two radiolytic substances produced during irradiation with an electron beam were predicted by LC-QTOF-MS. This study led to an understanding of the role of electron beams in the transformation of parent compounds and to the decomposition products created when an electron beam is applied to treat perfluorinated compounds.

Sorption of Nitro Explosives to Polymer/Biomass-Derived Biochar

Factors affecting the sorptive removal of nitro explosives (2,4,6-trinitrotoluene [TNT] and hexahydro-1,3,5-trinitro-1,3,5-triazine [RDX]) to polymer/biomass-derived biochar were investigated through batch experiments. Compared with that of rice ( L.) straw (RS)-derived biochar, the sorption of TNT and RDX to polymer/RS-derived biochar was greatly enhanced by >2.5 and 4 times, respectively. The type and amount of polymer did not significantly affect the sorption of nitro explosives to polymer/RS-derived biochar. Pyrolysis temperature did not affect the sorption capacity. Surface treatment with acid or an oxidant did not significantly change the sorption capacity, suggesting that polymer residues may be strongly responsible for the enhancement. Possible polymer residues were identified via gas chromatography mass spectrometry analysis. The toxicity characteristic leaching procedure and Microtox bioassay analyses indicated that polymer/RS-derived biochar did not show possible harmful effects. Our results suggest that polymer/RS-derived biochar can be effectively used as a sorbent to remove nitro explosives both in the natural environment and engineered systems.

Mode of action characterization for adverse effect of propranolol in Daphnia magna based on behavior and physiology monitoring and metabolite profiling

Studies are underway to gather information about the mode of action (MOA) of emerging pollutants that could guide practical environmental decision making. Previously, we showed that propranolol, an active pharmaceutical ingredient, had adverse effects on Daphnia magna that were similar to its pharmaceutical action. In order to characterize the mode of action of propranolol in D. magna, which is suspected to be organ-specific pharmaceutical action or baseline toxicity, we performed time-series monitoring of behavior along with heart rate measurements and nuclear magnetic resonance (NMR) based metabolite profiling. Principle component analysis (PCA) and hierarchical clustering were used to categorize the mode of action of propranolol among 5 chemicals with different modes of action. The findings showed that the mode of action of propranolol in D. magna is organ-specific and vastly different from those of narcotics, even though metabolite regulation is similar between narcotic and non-narcotic candidates. The method applied in this study seems applicable to rapid characterization of the MOA of other cardiovascular pharmaceutical ingredients.

Multigenerational Effects of the Antibiotic Tetracycline on Transcriptional Responses of Daphnia magna and Its Relationship to Higher Levels of Biological Organizations

Given the risk of environmental pollution by pharmaceutical compounds and the effects of these compounds on exposed ecosystems, ecologically relevant and realistic assessments are required. However, many studies have been mostly focused on individual responses in a single generation exposed to one-effect concentrations. Here, transcriptional responses of the crustacean Daphnia magna to the antibiotic tetracycline across multiple generations and effect concentrations were investigated. The results demonstrated that tetracycline induced different transcriptional responses of daphnids that were dependent on dose and generation. For example, reproduction-related expressed sequence tags (ESTs), including vitellogenin, were distinctly related to the dose-dependent tetracycline exposure, whereas multigenerational exposure induced significant change of molting-related ESTs such as cuticle protein. A total of 65 ESTs were shared in all contrasts, suggesting a conserved mechanism of tetracycline toxicity regardless of exposure concentration or time. Most of them were associated with general stress responses including translation, protein and carbohydrate metabolism, and oxidative phosphorylation. In addition, effects across the dose-response curve showed higher correlative connections among transcriptional, physiological, and individual responses than multigenerational effects. In the multigenerational exposure, the connectivity between adjacent generations decreased with increasing generation number. The results clearly highlight that exposure concentration and time trigger different mechanisms and functions, providing further evidence that multigenerational and dose-response effects cannot be neglected in environmental risk assessment.

Multigenerational effect of perfluorooctane sulfonate (PFOS) on the individual fitness and population growth of Daphnia magna

We investigated the multigenerational effect of PFOS to individual fitness (e.g., body weight, acetylcholinesterase and glutathione S-transferase) and population growth (e.g., offspring number and time to first brood) of Daphnia magna during continuous and discontinuous exposures. The intrinsic rate of population growth was also calculated. In the continuous exposure, population growth-related adverse effects were detected during all test periods, and the adverse effect tended to be weaker in later generations. On the other hand, individual fitness-related adverse effects were observed from F1 not in F0 and deteriorated as the generation number increased. These results imply that individual fitness worsens although the population growth is restored in later generations. Upon discontinuous exposure, a few but significant adverse effects were observed during the non-exposure period and highest effects were detected during the re-exposure period. This encourages the study of different exposure scenarios, which may result in unexpected and higher PFOS toxicity. Consequently, this study confirms adverse effects of PFOS to Daphnia magna in multigenerational period and supports reasons for studies linking individual fitness changes to population dynamics and covering diverse exposure scenarios to evaluate the risk of PFOS in a water environment.

Bioaccumulation and biotransformation of the beta-blocker propranolol in multigenerational exposure to Daphnia magna

Multigenerational bioaccumulation and biotransformation activity and short-term kinetics (e.g., uptake and depuration) of propranolol in Daphnia magna were investigated at environmental concentration. The body burden and the major metabolite, desisopropyl propranolol (DIP), of propranolol were quantified using LC-MS/MS at the end of each generation after exposure for 11 generations. The accumulation of propranolol in D. magna at an environmental concentration of 0.2 μg/L was not much different between the parent (F0) and the eleventh filial (F10) generation. However, at 28 μg/L, its accumulation was 1.6 times higher-up to 18.9 μg/g-in the F10 generation relative to the F0. In contrast to propranolol, DIP intensity gradually increased from F0 to F10 at 0.2 μg/L, reflecting an increase in detoxification load and biotransformation performance; no increasing trend was observed at 28 μg/L. The bioaccumulation factor (BAF) showed higher values with a lower concentration and longer period of exposure. The average values of the BAF for 21 days of long-term exposure in successive 11 generations were 440.4 ± 119.7 and 1026.5 ± 208.6 L/kg for 28 μg/L and 0.2 μg/L, respectively. These are comparable to the BAF of 192 for the short-term 72-h exposure at 28 μg/L in the parent generation. It is also recommended that future studies for pharmaceutical ingredients be conducted on drug-drug interaction and structural characteristics on the prediction of biotransformation activity and bioaccumulation rate.

Reduction and persulfate oxidation of nitro explosives in contaminated soils using Fe-bearing materials

The oxidative and reductive transformation of nitro explosives in contaminated soils with Fe-bearing materials and persulfate (S2O8(2-)) was examined via batch experiments. Zero-valent cast iron [Fe(0)], steel dust from a steel manufacturing plant, and FeS rapidly reduced 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in soil under anaerobic conditions as long as a sufficient amount of water was present. The Fe-bearing materials also effectively activated persulfate to enhance the oxidative transformation of TNT and RDX in soil-water systems. Kinetically, reductive and oxidative transformations removed more than 90% of the explosives from a soil-water system within 5 h under the given conditions. Pseudo-first-order rates in the range of 0.7-23.4 h(-1) were observed. By increasing the concentration of persulfate or Fe-bearing materials, the oxidative transformation could be promoted. Treated soils via redox reactions using the Fe-bearing materials did not show significant toxicity, except for the case of TNT-contaminated soils oxidized by FeS-assisted persulfate. Considering the kinetics of explosive degradation and the toxicity of treated wastewaters and soils, Fe(0) or steel dust-assisted persulfate oxidation may be a safe option as an ex situ remediation process for the treatment of explosive-contaminated soils.

Application of toxicity identification evaluation procedure to toxic industrial effluent in South Korea

Toxicity identification evaluation (TIE) was applied to the effluent from a pharmaceutical industrial complex, following the US EPA TIE guidelines. The whole effluent toxicity (WET) test found toxicity greater than 16toxic units (TU) in the effluent. Dissolved non-polar organic compounds were identified as the major contributor to the observed toxicity in the TIE manipulations in phases I and II. Among the 48 organic compounds identified, three compounds (i.e., acetophenone, benzoimide, and benzothiazole) were related to the pharmaceutical production procedure; however, no contribution to toxicity was predicted in the compounds. The results of the ECOSAR model, which predicts toxicity, indicated that the alkane compounds caused significant toxicity in the effluent. The toxicity test and heavy metal analysis, which used IC and ICP/MS, identified that particulate and heavy metals, such as Cu and Zn, contributed to the remaining toxicity, except dissolved organics. The results showed the applicability of the TIE method for predicting regional effluents produced by the industrial pharmaceutical complex in this study. Although the location was assumed to be affected by discharge of pharmaceutical related compounds in the river, no correlations were observed in the study. Based on the results, advanced treatment processes, such as activated carbon adsorption, are recommended for the wastewater treatment process in this location.

Sorption and toxicity reduction of pharmaceutically active compounds and endocrine disrupting chemicals in the presence of colloidal humic acid

This study investigated the toxicity changes and sorption of pharmaceuticals and endocrine disrupters in the presence of humic acid (HA). For the sorption experiment, a dead end filtration (DEF) system was used to separate bound and free-form target compounds. An algae growth inhibition test and E-screen assay were conducted to estimate the toxic effect of pharmaceutically active compounds (PhACs) and endocrine disrupting chemicals (EDCs), respectively. The permeate concentration was confirmed using liquid chromatography-mass spectrometry. In the sorption test, we observed significant sorption of PhACs and EDCs on colloidal HA, except for sulfamethoxazole (SMX). The values of log KCOC derived from DEF determinations ranged from 4.40 to 5.03. The removal efficiency varied with the HA concentration and the target chemical properties. Tetracycline and 4-octylphenol showed the highest sorption or removal efficiency (≈50%), even at 5 mg C/L HA. The algal growth inhibition of PhACs and the estrogenic effects of EDCs were significantly decreased in proportion to HA concentrations, except for SMX. In addition, the chemical analysis results showed a positive relationship with the bioassay results. Consequently, the sorption of PhACs and EDCs onto colloidal HA should be emphasized in natural environments because it significantly reduces bioavailable concentrations and toxicity to aquatic organisms.

Multi-generational effects of propranolol on Daphnia magna at different environmental concentrations

To evaluate the effects of propranolol on Daphnia magna (D. magna), we employed a multi-generational exposure period for eight generations and an environmentally relevant low concentration with 1.5 ng/L, 0.2 μg/L and 26 μg/L to reflect a realistic exposure scenario. Physiological endpoints were checked, including growth, number of neonates, heart rate, frequency of abdominal appendage movement and malformation rate of neonates. In the results, growth and abdominal appendage movement were affected by environmental concentration during several generations, and the responses showed consistent tendencies of response increase with concentration increase. Heart rate was the only endpoint affected throughout all exposure generations. Inhibitory and acceleratory effects on heart rate, growth and abdominal appendage movement suggest that it is necessary to cover sub-lethal endpoints of non-targeted organisms in eco-toxicity study because the physiological responses were detected at much lower concentrations than the results of traditional toxicity tests, including environmental concentration.

Putative type 1 thymidylate synthase and dihydrofolate reductase as signature genes of a novel Bastille-like group of phages in the subfamily Spounavirinae

Background

Spounavirinae viruses have received an increasing interest as tools for the control of harmful bacteria due to their relatively broad host range and strictly virulent phenotype.

Results

In this study, we collected and analyzed the complete genome sequences of 61 published phages, either ICTV-classified or candidate members of the Spounavirinae subfamily of the Myoviridae. A set of comparative analyses identified a distinct, recently proposed Bastille-like phage group within the Spounavirinae. More importantly, type 1 thymidylate synthase (TS1) and dihydrofolate reductase (DHFR) genes were shown to be unique for the members of the proposed Bastille-like phage group, and are suitable as molecular markers. We also show that the members of this group encode beta-lactamase and/or sporulation-related SpoIIIE homologs, possibly questioning their suitability as biocontrol agents.

Conclusions

We confirm the creation of a new genus—the “Bastille-like group”—in Spounavirinae, and propose that the presence of TS1- and DHFR-encoding genes could serve as signatures for the new Bastille-like group. In addition, the presence of metallo-beta-lactamase and/or SpoIIIE homologs in all members of Bastille-like group phages makes questionable their suitability for use in biocontrol.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1757-0) contains supplementary material, which is available to authorized users.

Complete genome sequence analysis and identification of putative metallo-beta-lactamase and SpoIIIE homologs in Bacillus cereus group phage BCP8-2, a new member of the proposed Bastille-like group

Bacillus cereus group-specific bacteriophage BCP8-2 exhibits a broad lysis spectrum among food and human isolates (330/364) of B. cereus while not infecting B. subtilis (50) or B. licheniformis (12) strains. Its genome is 159,071 bp long with 220 open reading frames, including genes for putative methyltransferases, metallo-beta-lactamase, and a sporulation-related SpoIIIE homolog, as wells as 18 tRNAs. Comparative genome analysis showed that BCP8-2 is related to the recently proposed Bastille-like phages, but not with either SPO1-like or Twort-like phages of the subfamily Spounavirinae.

Relationship between trans-generational effects of tetracycline on Daphnia magna at the physiological and whole organism level

The effects of pharmaceuticals have been underestimated during single generation exposure. Therefore, in this study, we investigated toxic responses at the physiological and whole organism level in tetracycline-exposed Daphnia magna over four consecutive generational lifecycles. The results showed that tetracycline affected energy-related physiological functions in concentration- and generation-dependent manners, and especially maintenance costs increased. Consequently, multigenerational exposure to tetracycline induced changes in energy balance, resulting in the change of higher levels of biological responses. In contrast, D. magna acclimated to tetracycline exposure over multiple generations, as evidenced by the increased LC50 values. Transgenerational adaptation was related to the neonatal sensitivity and energy reserves of the organism. The results also emphasized the idea that the number of generation is an important factor for toxicity. The present study confirmed that toxic stress induces metabolic changes in an organism, thereby leading to increased energy consumption that results in adverse effects on reproduction.