Use cases, best practice and reporting standards for metabolomics in regulatory toxicology

Metabolomics is a widely used technology in academic research, yet its application to regulatory science has been limited. The most commonly cited barrier to its translation is lack of performance and reporting standards. The MEtabolomics standaRds Initiative in Toxicology (MERIT) project brings together international experts from multiple sectors to address this need. Here, we identify the most relevant applications for metabolomics in regulatory toxicology and develop best practice guidelines, performance and reporting standards for acquiring and analysing untargeted metabolomics and targeted metabolite data. We recommend that these guidelines are evaluated and implemented for several regulatory use cases

Systems biology meets stress ecology: linking molecular and organismal stress responses in Daphnia magna

Background: Ibuprofen and other nonsteroidal anti-inflammatory drugs have been designed to interrupt eicosanoid metabolism in mammals, but little is known of how they affect nontarget organisms. Here we report a systems biology study that simultaneously describes the transcriptomic and phenotypic stress responses of the model crustacean Daphnia magna after exposure to ibuprofen. Results: Our findings reveal intriguing similarities in the mode of action of ibuprofen between vertebrates and invertebrates, and they suggest that ibuprofen has a targeted impact on reproduction at the molecular, organismal, and population level in daphnids. Microarray expression and temporal real-time quantitative PCR profiles of key genes suggest early ibuprofen interruption of crustacean eicosanoid metabolism, which appears to disrupt signal transduction affecting juvenile hormone metabolism and oogenesis. Conclusion: Combining molecular and organismal stress responses provides a guide to possible chronic consequences of environmental stress for population health. This could improve current environmental risk assessment by providing an early indication of the need for higher tier testing. Our study demonstrates the advantages of a systems approach to stress ecology, in which Daphnia will probably play a major role

Fundamental Studies of Humic Acid\u27s Influence on Pollutant Toxicity to Aquatic Organisms

The main purpose of the research presented in this dissertation was to further understand the intricate and convoluted interactions between natural organic material, biological entities, and pollutants. This was achieved by utilizing humic acids (HAs) from differing sources, chemically modified humic acid, two biological entities (model biomembranes and Artemia Franciscana), and three types of pollutants (cations, surfactants, and carbon nanotubes). Fluorescence spectroscopy and model biomembranes were used to measure the change in HA’s ability to interact with the biomembranes in the presence of cations. Three differently sourced HAs, chemical modified HAs, and a range of cations were studied to elucidate specific interactions that can occur in the environment. It was determined that the cations limited the ability of humic acids to interact with the biomembranes, which was attributed to humic acid conformation changes in the presence of cations, and the protection capacity increased as the softness of the cation increased. Artemia Franciscana (Artemia) was utilized as an analytic tool to determine the changes in toxicity of surfactants in the presence of humic acid. Artemia were exposed to three different surfactants, Triton X-100 (Tx-100), cetylpyridinium chloride (CPC), and sodium dodecyl sulfide (SDS), for both hatching studies and in vivo 31P NMR. It was determined by hatching assays that Tx-100 caused mortality after hatching while CPC and SDS inhibited hatching. 31P NMR corroborated these findings by showing an increase in phosphodiester bonds in saline water and in the Tx-100 exposure while there was no increase in the presence of the other two surfactants. HAs from three different sources were added to the surfactant exposures which showed that HAs played a mediation role in terms of toxicity and the extent of mediation was dependent on the type of HA and surfactant. Artemia was also utilized to measure the toxicity of carbon nanotubes under a variety of conditions. Both single-walled and multi-walled carbon nanotubes that were either in the presence of humic acid or had been sonicated were studied. Overall, there was no significant carbon nanotube toxicity to the Artemia

Biochemische und physiologische Mechanismen der Anpassung an variable Temperaturbedingungen bei Organismen des limnischen Zooplanktons

In der vorliegenden Arbeit wurden Untersuchungen zu den Mechanismen der Anpassung an unterschiedliche Temperaturbedingungen bei Zooplanktonorganismen durchgeführt und zwar bei Chaoborus crystallinus, Leptodora kindtii und Daphnia magna. Die räuberischen C. crystallinus-Larven und Leptodora kindtii wiesen unterschiedliche Thermotoleranzfenster auf. Der Toleranzbereich von C. crystallinus ist relativ breit (eurytherm) und die Thermotoleranz der Tiere scheint nicht sauerstofflimitiert zu sein. Das Thermotoleranzfenster von L. kindtii ist dagegen schmaler (stenotherm). Untersuchungen zum RNA- und DNA-Gehalt in D. magna zeigten temperaturabhängige Veränderungen in der Konzentration beider Nukleinsäuren. Bei 30 °C Inkubation war der RNA- und DNA-Gehalt viel größer als bei 10 und 20 °C Inkubation. Diese Befunde können entweder mit einem erhöhten Ploidiegrad der Zellkerne oder mit einer Chromatin-Reorganisation zusammenhängen, wobei letzteres eine größere Wahrscheinlichkeit besitzt

Ecological Constraints of Toxic Cyanobacterial Blooms

Toxic species of cyanobacteria form noxious blooms in freshwater ecosystems that provide critical drinking water, fisheries, and recreational needs worldwide. Blooms are caused principally by nutrient over-enrichment of water bodies and are exacerbated by increasing temperatures caused by global climate change. Blooms have increased in frequency and severity due to changes in land use and climate patterns that are projected to continue or accelerate in the future. Against this backdrop, there is a need for improved understanding of the ecological constraints governing cyanobacterial blooms. This dissertation presents studies addressing several aspects of this question. We demonstrated that seasonally-relevant cool temperatures dramatically increase microcystin quota in lab cultures of Microcystis aeruginosa NIES-843, providing an additional explanation for the observed pattern in which blooms tend to have higher toxin content in spring relative to mid-summer. Data from monitoring stations in Lake Erie illustrate the potential for incorporating a temperature-driven toxin phenotype into bloom prediction models. Following speculation in the literature and using E. coli as a model organism, we tested the hypothesis that microcystin-LR serves as an allelopathic agent against heterotrophic bacteria by means of inducing oxidative and envelope stress within these bacteria. We found no evidence to support this hypothesis, casting doubt on this putative role, at least for bacteria whose response is similar to E. coli. To facilitate additional research into the viral ecology of Cylindrospermopsis blooms, we sequenced and analyzed the genomes of Cylindrospermopsis raciborskii Virus (CrV) and its host C. raciborskii Cr2010. We show that CrV likely represents a clade of viruses infecting and perhaps lysogenizing filamentous cyanobacteria. Metagenomic data indicates CrV-like viruses are distributed across distant locals. The CrV genome is unique in containing an intact CRISPR array and an unusual 12-kb inverted repeat. The host genome contains a CRISPR-Cas system targeting the genome of CrV, but is apparently non-functional, perhaps due to lack of a key gene. Collectively, these features make CrV/Cr2010 an exciting system in which to investigate virus/host interactions in a bloomforming cyanobacterium