Environmental metabolomics helps to study the impact on organisms when exposed to environmental stress such as pollution, changes in climate, infection, or a combination of these stressors. Environmental metabolomics, which encompasses plants and animals, both terrestrial and aquatic, and humans, assists us in monitoring the environment and assessing the risks involved in the ecology.
Metabolomic studies have greater potential in assessing the toxic effects of environmental pollutants on terrestrial organisms and the associated health risks when exposed to a variety of contaminants.
Studies of rat urine have revealed the capabilities of metabolomics in biomonitoring. Considerable metabolite changes were reported when the species Mus musculus were exposed to Dechlorane Plus (DP), a highly chlorinated flame retardant.
As earthworms are relied on as indicators of the health and toxicity of soil, numerous studies have been conducted on earthworms to assess the health of the soil.
- Species such as Eisenia andrei, Lumbricus rubellus, Eisenia veneta, Lumbricus terrestris, and Aporrectodea caliginosa are used in analyzing contaminants in the soil.
- The organization for economic cooperation and development (OECD) has suggested to use earthworm species Eisenia fetida for testing ecotoxicity. Exposing E. fetida to environmental contaminants such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) has found the possibility of an increase in fatty acid oxidation. While exposing to polyaromatic hydrocarbon contaminants such as phenanthrene, it was found that the earthworm species E. fetida shows a lower metabolic response in soils of high organic carbon content. These studies demonstrate the role of metabolomics in explaining contaminant action approaches and help in assessing the health of the soil.
- Exposing species L. rubellus to thiacloprid/imidacloprid and nickel/chlorpyrifos has yielded distinctive responses for each of the pollutants. This proves the capability of metabolomics in finding significant reactions when exposing organisms to a contaminant mixture. Metabolomic studies assessing polluted environments have determined the elicit response of earthworms when exposed to a main contaminant, zinc.
- Environmental stressors such as organic pollutants, heavy metal, or heat can alter the gene expression patterns in microorganisms. Studies on nicotine exposure in Pseudomonas sp. HF-1 have found hampered nucleotide biosynthesis and a slower exponential growth phase. Pyrimidine, putrescine, succinate, trehalose, glutamate, and glucose were recognized as metabolite biomarkers when exposed to nicotine.
- Metabolomics analysis for cold tolerance in tissue extracts of fruit fly Drosophila melanogaster has revealed an increase in sugar levels such as fructose, trehalose, and sucrose and a rise in polyamines such as putrescine and cadaverine. There is also a decrease seen in metabolic intermediates fumarate, citrate, glycerate, and malate, indicating a decrease in energy metabolism. Fruit flies use the drop in energy metabolism as an approach to save energy after cold acclimation.
Several studies focused on fish metabolomics have analyzed a variety of fish species such as flatfish, rainbow trout, fathead minnows, Chinook salmon, topsmelt, Japanese medaka, freshwater carp, zebrafish, Atlantic salmon, sharks, and whales. Since the biochemical mechanisms are similar in humans and fish, ecotoxicity studies of fish are useful, particularly in the field of pharmaceuticals.
- In a study involving fathead minnows, while analyzing the behavior pattern in sexual selection it was found that the metabolites taurocholic acid and trimethylamine were higher in dominant males promising developments in behavioral ecology.
The ease of handling and transporting to other areas, their sedentary nature, and capability to accumulate toxins has paved the way to focus studies on mollusk species. Research conducted on species such as green mussel, red abalone, Asian clam, blue mussel, and Mediterranean mussel have been found beneficial in studying ecotoxicity.
- Exposing Mediterranean mussel and Mytilus species to polycyclic aromatic hydrocarbon has seen a rise in anaerobic metabolism.
- Exposure of Diporeia species to atrazine has found increase of hydrocarbons, heptacosane and nonadecane, which is important in carapace exuviations.
- Exposing Daphnia magna to contaminated pyrene and sublethal fluoranthene has discovered disruptions in the metabolism of aminosugar.
Image: Oil in water, water pollution.
Applications in Aquaculture
The quality of hatchery production is a matter of concern as technical developments are not captured well. Metabolomic studies are in progress to examine the larvae stage of aquatic organisms such as fish and other marine invertebrates. The physiological conditions of the larvae are studied using the metabolomics approach to assess their quality. Metabolite profiles of slow and fast growing larvae are obtained. The correlation of diet in production yields such as effects of food deprivation, connections between food, disease, and environment, role of nutritional supplements are also being studied. There is evidence of assessing the ability of organisms such as Carassius auratus to survive bacterial infections caused by Edwardsiella tarda.
Metabolomic studies have been carried out on aquatic plants such as Eurasian watermilfoil and common duckweed. Variations have been noticed in the metabolome of plants reared under controlled conditions while comparing with those plant samples caught wild. The lab-controlled samples reported less intraspecific variations as they were grown under a more predictable and controlled environment. These results could be helpful to monitor organisms and understand the health of the environment.
Reviewed by Afsaneh Khetrapal BSc (Hons)