Ethylene regulates plant root growth and resistance to environment stress. However, the role and mechanism of ethylene signaling in response to Cd stress in rice remains unclear. Here, we revealed that ethylene signaling plays a positive role in the resistance of rice to Cd toxicity. Blocking the ethylene signal facilitated root elongation under normal conditions, but resulted in severe oxidative damage and inhibition of root growth under Cd stress. Conversely, ethylene signal enhancement by EIN2 overexpression caused root bending, similar to the response of roots to Cd stress, and displayed higher Cd tolerance than the wildtype (WT) plants. Comparative transcriptome analysis indicated EIN2-mediated upregulation of genes involved in flavonoid biosynthesis and peroxidase activity under Cd stress. The synthesis of phenolic acids and flavonoids were positively regulated by ethylene. Thus, the ein2 (ethylene insensitive 2) mutants displayed lower ROS scavenging capacity than the WT. Moreover, a significant increase in Cd accumulation and relatively increased apoplastic flow were observed in the root apex of the ein2 mutant compared with the WT plants. Overall, EIN2-mediated Cd resistance in rice is mediated by the upregulation of flavonoid biosynthesis and peroxidase activity to induce ROS scavenging, and apoplastic transport barrier formation reduces Cd uptake.

The abuse or misuse of antibiotics is directly linked to the emergence of antibiotic-resistant bacteria and antibiotic resistance genes (ARGs) in the environment. Most fish farms located on Jeju Island operate a flow-through system that pumps in seawater for fish farming and discharges it back to the ocean. To investigate the amount of ARGs that these fish farm effluents discharge into the marine environment, we conducted a metagenomic-based resistome analysis. We observed higher levels of ARGs in fish farm effluents than in seawater at beach and residential areas. A greater proportion of ARGs was found on plasmid rather than on chromosomal DNA, especially for sulfonamide and phenicol classes. The distribution of ARGs did not differ between summer and winter, but the microbial community did. In addition, fish farm samples contained significantly more opportunistic pathogens (i.e., Vibrio, Photobacterium, Aliivibrio, and Tenacibaculum) and virulence factors than non-fish farm samples. Vibrio was the most frequently identified host of ARGs and virulence factors. The presence of Vibrio in the coastal area has been increasing owing to the recent rise in the temperature of seawater. This study suggests the need for actions to treat or monitor ARGs in the coastal areas where fish farms operating a flow-through system are located.

Residues of glyphosate (GLY) are widely detected in aquatic systems, raising potential environmental threats and public health concerns, but the mechanism underlying GLY-induced hepatotoxicity in fish has not been fully elucidated yet. This study was designed to explore the hepatotoxic mechanism using juvenile common carp exposed to GLY for 45 d, and plasma and liver samples were collected at 15 d, 30 d, and 45 d to analyze the assays. First, GLY-induced hepatic damage was confirmed by serum liver damage biomarker and hepatic histopathological analysis. Next, changes in oxidative stress biomarkers, gene expression levels of pro- and anti-inflammatory cytokines, and lipid metabolism-related parameters in collected samples were analyzed to clarify their roles in GLY-induced hepatic damage. Data showed that oxidative stress was an early event during GLY exposure, followed by hepatic inflammatory response. Lipid metabolism disorder was a late event during GLY exposure, as evidenced by overproduced hepatic free fatty acids, enhanced lipogenesis-related gene expression levels, reduced lipolysis-related gene expression levels, and resultant hepatic lipid accumulation. Collectively, these findings demonstrate that GLY induces hepatotoxicity in fish through involvement of oxidative stress, inflammatory response, and lipid metabolism disorder, which are intimately interrelated with each other during GLY exposure.

Evidence about the adverse effects of methamphetamine (METH) on invertebrates is scarce. Hence, C. elegans, a representative invertebrate model, was exposed to METH at environmental levels to estimate chronic and transgenerational toxicity. The results of chronic exposure were integrated into an underlying toxicity framework of METH in invertebrates (e.g., benthos) at environmentally relevant concentrations. The induction of cellular oxidative damage-induced apoptosis and fluctuation of ecologically important traits (i.e., feeding and locomotion) might be attributed by the activation of the longevity regulating pathway regulated by DAF-16/FOXO, and detoxification by CYP family enzymes. The adverse effects to the organism level included impaired viability and decreased fecundity. The results from transgenerational exposure elucidated the cumulative METH-induced damage in invertebrates. Finally, a new risk assessment method named toxicity indicator sensitivity distribution (TISD) analysis was proposed by combining multiple toxicity indicator test data (ECₓ) to derive the hazardous concentration for 10% indicators (C₁₀) of one species. The risk quotient (RQ) values calculated by measured environmental concentrations and C₁₀ in southern China, southeastern Australia, and the western US crossed the alarm line (RQ = 5), suggesting a need for long-term monitoring.

Microbial source tracking (MST) DNA-based assays have been used to successfully solve fecal pollution problems in many countries, particularly in developed nations. However, their application in developing countries has been limited but continues to increase. In this study, sixteen endpoint and quantitative PCR (qPCR) assays targeting universal and human-, swine-, and cattle-specific Bacteroidales gene markers were modified for endpoint PCR, evaluated for their performance with sewage and fecal samples from the Tha Chin watershed and subsequently validated with samples from the Chao Phraya watershed, Thailand. Sample sizes of 81 composite samples (from over 1620 individual samples) of farm animals of each type as well as 19 human sewage samples from the Tha Chin watershed were calculated using a stratified random sampling design to achieve a 90% confidence interval and an expected prevalence (i.e., desired assay's sensitivity) of 0.80. The best universal and human-, swine-, and cattle-specific fecal markers were BacUni EP, HF183/BFDrev EP, Pig-2-Bac EP, and Bac3 assays, respectively. The detection limits for these assays ranged from 30 to 3000 plasmid copies per PCR. The positive predictive values were high in universal and swine- and cattle-specific markers (85–100%), while the positive predictive value of the human-specific assay was 52.2%. The negative predictive values in all assays were relatively high (90.8–100%). A suite of PCR assays in Thailand was established for potential MST use in environmental waters, which supports the worldwide applicability of Bacteroidales gene markers. This study also emphasizes the importance of using a proper sample size in assessing the performance of MST markers in a new geographic region.

One of the fundamentals in the ecotoxicological studies is the need of data comparison, which can be easily reached with the help of a standardized biological model. In this context, any biological model has been still proposed for the biomonitoring and risk evaluation of freshwaters until now. The aim of this review is to illustrate the ecotoxicological studies carried out with the zebra mussel Dreissena polymorpha in order to suggest this bivalve species as possible reference organism for inland waters. In detail, we showed its application in biomonitoring, as well as for the evaluation of adverse effects induced by several pollutants, using both in vitro and in vivo experiments. We discussed the advantages by the use of D. polymorpha for ecotoxicological studies, but also the possible limitations due to its invasive nature.

Bisphenol A (BPA) is widely used industrially to produce polycarbonate plastics and epoxy resins. Numerous studies document the harmful effects caused by low-dose BPA exposure especially on nervous systems and behavior in experimental animals such as mice and rats. Here, we exposed embryos of a model chordate, Ciona intestinalis, to seawater containing BPA to evaluate adverse effects on embryonic development and on the swimming behavior of subsequent larvae. Ciona is ideal because its larva develops rapidly and has few cells. The rate of larval hatching decreased in a dose-dependent manner with exposures to BPA above 3 μM; swimming behavior was also affected in larvae emerging from embryos exposed to 1 μM BPA. Adverse effects were most severe on fertilized eggs exposed to BPA within 7 h post-fertilization. Ciona shares twelve nuclear receptors with mammals, and BPA is proposed to disturb the physiological functions of one or more of these.

Ground–level ozone (O3) is known to exhibit strong daily variations that lead to complexity of the pollutants’ analysis and predictions. This study aimed to introduce and explore the variations in O3 concentrations during daytime (DT), nighttime (NT), and critical conversion time (CCT) using multiple linear regression (MLR) and principal component regression (PCR) analyses. The original variables and principal component analysis (PCA) results were used as the input for MLR analysis. Hourly averages of six air pollutants and four meteorological parameters at Shah Alam during 1999–2009 were selected for this study. The monitoring records in 2010 were used to assess the developed models using several performance indicators. Results showed that the MLR model during DT exhibited optimal performance in terms of normalized absolute error, index of agreement, prediction accuracy, and coefficient of determination (R2) with values of 0.2762, 0.9211, 0.8581, and 0.7354, respectively. PCR during CCT also showed significantly higher performance than that during DT and NT. This result was evidenced by higher percentage of total variances, which could be explained by the selected variables in PCA during CCT.

Analyses of thermotolerant coliform and heterotrophic bacteria as well as Escherichia coli and Vibrio species were carried out on plastic samples and in the surrounding waters of Guanabara Bay to evaluate plastic debris as vehicles of bacterial dispersal. Chemical characterizations of plastics were performed using Fourier transform infrared spectroscopy (FTIR). Plastic debris with high coliform contents were found, while their respective water samples had only low titers. No correlations were observed, however, between the amounts of bacteria and the chemical compositions of the plastic debris. Forty-four bacterial strains were PCR-confirmed as E. coli pathotypes, and 59 strains of Vibrio spp. (with 12 being identified as Vibrio cholerae [6], Vibrio vulnificus [5], and Vibrio mimicus [1]). These findings suggest these plastics can function as a substrate for bacterial biofilms (including pathogens). These debris, in turn, can be dispersed in aquatic environments not otherwise showing recent fecal bacterial contamination.

The aims of this study were to investigate the presence of Staphylococcus aureus and staphylococcal enterotoxins, as well as Salmonella spp. and to determine the antimicrobial susceptibilities of the isolates from fish samples. A total of 100 fish samples were analysed consisting of 30 anchovy, 35 trout and 35 sea bream. The presence of SEs was detected using ELISA and its genes confirmed by mPCR. Also, S. aureus and Salmonella spp. were detected in 9 (9%) and 5 (5%) samples, respectively. None of the S. aureus isolates had SEs and SEs genes. The resistance rates of the S. aureus isolates to erythromycin, tetracycline, and penicillin G were found to be 33% while Salmonella spp. isolates were resistant to trimethoprim-sulfamethoxazole, gentamicin and neomycine in 20%, 20% and 80%, respectively of the samples. It is of utmost important for public health that retail fish markets need to use hygienic practices in handling and processing operations.