Metabolite tracking to elucidate the effects of environmental pollutants.

The purpose of this study was to determine whether behavioral tests and metabolic profiling of organisms can be promising alternatives for assessing the health of aquatic systems. Water samples from four potential pollution sources in South Korea were collected for toxicity evaluation. First, conventional acute toxicity test in Daphnia magna and behavioral test in zebrafish was conducted to assess water quality. Second, metabolomic analysis was performed on zebrafish exposed to water samples and on environmental fish collected from the same source. Acute toxicity test in D. magna showed that none of the water samples exerted significant adverse effects. However, activity of zebrafish larvae exposed to samples from the zinc smelter (ZS) and industrial complex (IND) sites decreased compared to those exposed to samples from the reference site (RS). Metabolomic analysis using the Manhattan plot and Partial Least Square (PLS)/Orthogonal PLS Discriminant Analysis (OPLS-DA) showed differences in metabolic profiles between RS and ZS, and between IND and abandoned mine site (M). Interestingly, applying the same metabolomic analysis to environmental fish revealed patterns similar to those for zebrafish, despite the uncontrollable variables involved in environmental sampling. This study shows that metabolomics is a promising tool in assessing the health of aquatic environments.

Effects of nanoscale zero valent iron (nZVI) concentration on the biochemical conversion of gaseous carbon dioxide (CO2) into methane (CH4).

This study presents the effects of nanoscale zero valent iron (nZVI) concentration on the biomethanation of gaseous CO2. During anaerobic batch experiment with 9 times injection of CO2, the CO2 concentration in the headspace rapidly decreased by dissolution. Then, when nZVI was added at 6.25 and 12.5 g/L, the dissolved CO2 was biochemically transformed into CH4 at a maximum production rate of 2.38 and 3.93 µmol/hr, respectively. Biomethanation at these two nZVI concentrations continued until the end of experiment. In spite of more H2 evolution by nZVI at 25 g/L, biomethanation did not occur, due to the significant inhibition of methanogenesis by nZVI. As the nZVI concentration increased, relative abundance of the hydrogenotrophic methanogens, especially Methanobacteriales, increased. However, at 25 g/L of nZVI concentration, acetic acid was accumulated and the relative abundance of Clostridium became predominant, indicating that homoacetogenesis was superior over methanogenesis.

Seasonal Changes in Antibiotic Resistance Genes in Rivers and Reservoirs in South Korea.

The fate of antibiotic resistance genes (ARGs) in aquatic environments, especially in rivers and reservoirs, is receiving growing attention in South Korea because reservoirs are an important source of drinking water in this country. Seasonal changes in the abundance of 11 ARGs and a mobile genetic element () in two reservoirs in South Korea, located near drinking water treatment plants in Cheonan and Cheongju cities, were monitored for 6 mo. In these drinking water sources, total ARG concentrations reached 2.5 × 10 copies mL, which is one order of magnitude higher than in influents of some wastewater treatment plants in South Korea. During the sampling periods in August, October, and November 2016 and January 2017, sulfonamides (), ß-lactam antibiotics (), and tetracycline () resistance genes were the most abundant genes at the two sites. The ARG abundance consistently increased in January relative to 16S ribosomal ribonucleic acid (rRNA) counts. General stress responses to oxidative stress and other environmental factors associated with the cold season could be significant drivers of ARG horizontal gene transfer in the environment. Accordingly, removal of ARGs as a key step in water treatment warrants more attention.