Project description:Small organisms can be used as biomonitoring tools to assess chemicals in the environment. Chemical stressors are especially hard to assess and monitor when present as complex mixtures. Here, Daphnia magna were exposed for 24 hours to five different munitions constituents 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (2,4-DNT), 2,6-dinitrotoluene (2,6-DNT), trinitrobenzene (TNB), dinitrobenzene (DNB), or 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) as well as to 8 different munitions mixtures and ground water contaminated with munitions constituents. To better understand possible mixture effects, gene expression changes from all treatments were compared using high-density microarrays. While mixtures and ground water exposures had genes and gene functions in common with single chemical exposures, unique functions were also affected, which was consistent with the non-additivity of chemical effects in these mixtures. The study consisted of three different experiments: (1) exposure to a concentration corresponding to 70% of 1/10th of the LC50 value of six individual MCs (TNT, 2,4-DNT, 2,6-DNT, DNB, TNB, RDX) and a control; (2) exposure to eight different laboratory mixtures of the previously mentioned MCs. Different combinations of MCs including four mixtures (Mixtures 5, 6, 7 and 8) representative of field collected groundwater from LAAP (Louisiana Army Ammunition Plant) were created; and (3) exposure to MC-contaminated ground water field-collected from 3 different wells (85, 108, and 141) at the LAAP. All exposures were conducted for 24h.
Project description:In the past years, the research focus on the effects of microplastics (MP) on aquatic organisms extended from marine systems towards freshwater systems. An important freshwater model organism in the MP field is the cladoceran Daphnia, which plays a central role in lacustrine ecosystems and has been established as a test organism in ecotoxicology. To investigate the effects of MP on Daphnia magna, we performed a chronic exposure experiment with polystyrene MP under strictly standardized conditions. Chronic exposure of D. magna to PS microparticles led to a significant reduction in body length and number of offspring. To shed light on underlying molecular mechanisms induced by microplastic ingestion in D. magna, we assessed the effects of PS-MP at the proteomic level.
Project description:Background: Toxicogenomics provides new opportunities for innovative and proactive approaches to chemical screening, risk assessment, and predictive toxicology. If applied to ecotoxicology, genomics tools could greatly enhance the ability to detect toxicants and understand the modes of toxicity in an environmental setting. However, few studies have yet to illustrate the potential of genomic techniques in ecotoxicology. Objective: Therefore, our objective was to demonstrate the potential utility of gene expression profiling in ecotoxicology using Daphnia magna, a standard aquatic ecotoxicity test organism. Methods: D. magna were exposed to copper, cadmium, and zinc at the 1/10 LC50 for 24 hours. Following each exposure, RNA was isolated, reverse transcribed, and the cDNA was hybridized to a 5000 clone cDNA microarray for D. magna. Differentially expressed cDNAs were sequenced and homology searches revealed each gene product's potential function. Real time PCR was used to verify the differential expression of several genes, and enzyme assays were used to assess the significance of these changes. Results: We identified distinct expression profiles in response to acute copper, cadmium, and zinc exposures and discovered specific biomarkers of exposure including two probable metallothioneins, and a ferritin mRNA with a functional IRE. The gene expression patterns support known mechanisms of metal toxicity and reveal novel modes of action including zinc inhibition of chitinase activity. Conclusions: Using a cDNA microarray for traditional ecotoxicology organism, D. magna, we have identified novel biomarkers of exposure and revealed possible modes of toxicity, providing experimental support for the utility of ecotoxicogenomics. Keywords: comparative toxicant exposure
Project description:Transcriptomic profiling of Daphnia magna samples exposed to tributyltin (TBT), pyriproxyfen (PP) and bisphenol A (BPA) at 8 and 24 hours. The analysis of lipid disruptive effects in invertebrates is limited by our poor knowledge of their lipidomes and of the associated metabolic pathways. Here we analyzed the subsequent transcriptome changes, using tributyltin (TBT), pyriproxyfen (PP) and bisphenol A (BPA). Changes in the whole transcriptome were assessed after 8 and 24 h of exposure, the period showing the greatest variation in storage lipid accumulation. The three compounds affected similarly to a total of 1388 genes (965 overexpressed and 423 underexpressed transcripts), but only after 24h of exposure. In addition,225 transcripts became up-regulated only in samples exposed to tributyltin for both 8h and 24 h. Using functional annotation from D. melanogaster, we determined that upregulated genes were enriched in members of KEGG modules implicated in fatty acid, phosphoinositol, glycerophospholipid, and glycerolipid metabolic pathways, as well as in genes related to membrane constituents , and to chitin and cuticle metabolic pathways. Conversely, down-regulated genes appeared mainly related with to visual perception, and to oocyte development signalling pathways. Many tributyltin specifically upregulated genes were related to neuro-active ligand receptor interaction signalling pathway. These changes are consistent with the previous observation that exposure of D. magna to the tested compounds increases lipid accumulation and reduces egg quality.