The anthropogenic activities, including municipal and industrial sewage, contaminated wastes from mining, petroleum-related activities, and agriculture runoff, make a huge threat to environmental resources conservation. Among them, pollutant discharges from mining and other sources have led to metal bioaccumulation, and thereby posing serious ecotoxicity issues. Metals are persistent environmental contaminants that have adversely impact human health, such as developmental and behavioral deficits and neurodegeneration. Many metals, including Zn, Mn, and Fe, play critical roles in cell viability and function. Although metals have physiologic roles, the excessive levels of metals can be deleterious. Metals can pose protein and DNA oxidation and lipid peroxidation through generating free radicals and reactive oxygen species (ROS).

A biosensor of environmental pollution by metals

As a free-living soil nematode, C. elegans lives in the film of water around soil particles and feeds mainly on bacteria in decaying matter such as compost. Simultaneously, as a test organism, C. elegans is an attractive model for high throughput screens and characterized by its small size, its short lifespan, ease of manipulation and storage in the laboratory, low cost, and high homology with humans. Therefore it is suitable for toxicity testing in both aquatic and soil environments and initially used for aquatic testing of metal toxicity in 1990. The advantages of C. elegans have been extensively exploited in ecotoxicology over the past two decades.

Biomarkers for the diagnosis of metal contamination in C. elegans

Importantly, C. elegans contains plenty of stress and transporters response genes that are critical for metal detoxification, with respect to metallothioneins (MTs), heat shock proteins (HSPs), transporters involved in metal homeostasis. For example, C. elegans can make high response to metals by expressing metallothioneins, the small cysteine-rich proteins within strong affinity to metals, referring to several pathways, such as metal detoxification, and protection against oxidant agents. The heat shock proteins induced by high doses of metals work as molecular chaperones, not only supporting refolding and restoring of denatured proteins but also aiding protein synthesis. Therefore, numerous studies have established the utility of transgenic C. elegans strains as biosensors of metal pollution, using well-characterized metallothionein (including mtl-1and mtl-2) and heat-shock (hsp-16.1 and hsp-16.2) output genes as suitable biomarkers for the diagnosis of metal contamination. And the approach is extendedly facilitated by the use of green fluorescence protein (GFP) reporter system. It is notable that using multiple GFP stress-reporter strains can provide an outline map of the patterns of gene expression when exposed to toxic environmental chemicals, both singly and in mixtures.

Additionally, for C. elegans, the detoxification of metal stress involves various enzyme activities, including glutathione peroxidases (GPxs), superoxide dismutases (SODs), glutathione-S-transferases (GSTs), and cytochromes P450 (CYPs). These enzymes play important roles in the process of detoxification. For example, GPxs belong to the first line of defense against peroxides, hydrogen peroxide, and superoxide anion. SODs protect cells from oxidative damage and the sod-1and sod-4 are reportedly used for the determination of Cu and Zn. Therefore, the transgenic strains containing these genes are also applied to assist the diagnosis of metal pollution.

CD BioSciences is dedicated to providing the best service to accelerate the achievement of our customers’ research goals. As a useful bioindicator of environmental disturbances, C. elegans frequently is used in ecotoxicological studies, especially determination of environmental pollution by metals in both aquatic and soil environments. Although we focuses on metal effects, the nematodes are also used on pesticides and other environmental toxicants. Here we are dedicated to providing a systematic platform to develop a screening system for ecotoxicity monitoring. Please feel free to contact us if you would like to know more details of our services.

Reference

1. Anbalagan C, et al. (2012). "Transgenic nematodes as biosensors for metal stress in soil pore water samples". Ecotoxicology. 21(2):439-455.

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