New Insights on Ecosystem Mercury Cycling Revealed by Stable Isotopes of Mercury in Water Flowing from a Headwater Peatland Catchment

Stable isotope compositions of mercury (Hg) were measured in the outlet stream and in soil cores at different landscape positions in a 9.7-ha boreal upland-peatland catchment. An acidic permanganate/persulfate digestion procedure was validated for water samples with high dissolved organic matter (DOM) concentrations through Hg spike addition analysis. We report a relatively large variation in mass-dependent fractionation (δ²⁰²Hg; from −2.12 to −1.32‰) and a smaller, but significant, variation of mass-independent fractionation (Δ¹⁹⁹Hg; from −0.35 to −0.12‰) during two years of sampling with streamflow varying from 0.003 to 7.8 L s^–1. Large variations in δ²⁰²Hg occurred only during low streamflow (<0.6 L s^–1), which suggest that under high streamflow conditions a peatland lagg zone between the bog (3.0 ha) and uplands (6.7 ha) becomes the dominant source of Hg in downstream waters. Further, a binary mixing model showed that except for the spring snowmelt period, Hg in streamwater from the catchment was mainly derived from dry deposition of gaseous elemental Hg (73–95%). This study demonstrates the usefulness of Hg isotopes for tracing sources of Hg deposition, which can lead to a better understanding of the biogeochemical cycling and hydrological transport of Hg in headwater catchments

Proteogenomic Analyses Revealed Favorable Metabolism Pattern Alterations in Rotifer <i>Brachionus plicatilis</i> Fed with Selenium-rich <i>Chlorella</i>

Organoselenium have garnered attention because of their potential to be used as ingredients in new anti-aging and antioxidation medicines and food. Rotifers are frequently used as a model organism for aging research. In this study, we used Se-enriched <i>Chlorella</i> (Se-<i>Chlorella</i>), a novel organoselenium compound, to feed <i>Brachionus plicatilis</i> to establish a rotifer model with a prolonged lifespan. The results showed that the antioxidative effect in Se-enriched rotifer was associated with an increase in guaiacol peroxidase (GPX) and catalase (CAT). The authors then performed the first proteogenomic analysis of rotifers to understand their possible metabolic mechanisms. With the de novo assembly of RNA-Seq reads as the reference, we mapped the proteomic output generated by iTRAQ-based mass spectrometry. We found that the differentially expressed proteins were primarily involved in antireactive oxygen species (ROS) and antilipid peroxidation (LPO), selenocompound metabolism, glycolysis, and amino acid metabolisms. Furthermore, the ROS level of rotifers was diminished after Se-<i>Chlorella</i> feeding, indicating that Se-<i>Chlorella</i> could help rotifers to enhance their amino acid metabolism and shift the energy generating metabolism from tricarboxylic acid cycle to glycolysis, which leads to reduced ROS production. This is the first report to demonstrate the anti-aging effect of Se-<i>Chlorella</i> on rotifers and to provide a possible mechanism for this activity. Thus, Se-<i>Chlorella</i> is a promising novel organoselenium compound with the potential to prolong human lifespans

Proteogenomic Analyses Revealed Favorable Metabolism Pattern Alterations in Rotifer <i>Brachionus plicatilis</i> Fed with Selenium-rich <i>Chlorella</i>

Organoselenium have garnered attention because of their potential to be used as ingredients in new anti-aging and antioxidation medicines and food. Rotifers are frequently used as a model organism for aging research. In this study, we used Se-enriched <i>Chlorella</i> (Se-<i>Chlorella</i>), a novel organoselenium compound, to feed <i>Brachionus plicatilis</i> to establish a rotifer model with a prolonged lifespan. The results showed that the antioxidative effect in Se-enriched rotifer was associated with an increase in guaiacol peroxidase (GPX) and catalase (CAT). The authors then performed the first proteogenomic analysis of rotifers to understand their possible metabolic mechanisms. With the de novo assembly of RNA-Seq reads as the reference, we mapped the proteomic output generated by iTRAQ-based mass spectrometry. We found that the differentially expressed proteins were primarily involved in antireactive oxygen species (ROS) and antilipid peroxidation (LPO), selenocompound metabolism, glycolysis, and amino acid metabolisms. Furthermore, the ROS level of rotifers was diminished after Se-<i>Chlorella</i> feeding, indicating that Se-<i>Chlorella</i> could help rotifers to enhance their amino acid metabolism and shift the energy generating metabolism from tricarboxylic acid cycle to glycolysis, which leads to reduced ROS production. This is the first report to demonstrate the anti-aging effect of Se-<i>Chlorella</i> on rotifers and to provide a possible mechanism for this activity. Thus, Se-<i>Chlorella</i> is a promising novel organoselenium compound with the potential to prolong human lifespans