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Comprehensive Assessment of Germline Chemical Toxicity Using the Nematode Caenorhabditis elegans
Published on: February 22, 2015
RNA/DNA ratios as a sublethal endpoint for large-scale toxicity tests with the nematode Caenorhabditis elegans
1Centre for Ecology, Evolution, and Conservation (CEEC), School of Environmental Science, University of East Anglia, NR4 7TJ, United Kingdom.
Abstract:
Caenorhabditis elegans increasingly is attractive as a toxicity test organism, particularly as a model system to study mechanisms of toxicity at a molecular level and the way that these lead to whole organism and population level effects. Inhibitions of growth, reproduction, movement, and feeding rate all have been proposed as sublethal toxicity endpoints. These endpoints are more sensitive than 24-h acute toxicity endpoints, but assays are much more time consuming, making them difficult to use in mass screening. The RNA/DNA ratio, after 48-h exposure to metals, has median effective concentration (EC50) values of 0.05, 0.6, 6.1, and 35 mg/L for Cu, Pb, Cd, and Zn, respectively. This makes it a slightly more sensitive toxicity endpoint than reduction of individual growth after 72-h exposure to the same concentrations. This facilitates the near-simultaneous assessment of sublethal toxicity in many nematode samples. The constant cell number of C. elegans means that different stages in the life history have very different RNA/DNA ratios even in the absence of toxins. So, RNA/DNA ratios can be used only on prereproductive, age-synchronized cultures. Assessing the sublethal toxicity of metals to C. elegans shows that it is sensitive particularly to Cu.
Insights
Caenorhabditis elegans offers a sensitive method for toxicity testing using the RNA/DNA ratio. This approach effectively assesses sublethal metal toxicity, particularly copper, in nematodes.
Area of Science:
- Environmental toxicology
- Molecular biology
- Nematology
Background:
- Caenorhabditis elegans is a valuable model organism for studying toxicity mechanisms from molecular to population levels.
- Sublethal endpoints like growth and reproduction inhibition are sensitive but time-consuming for mass screening.
- The RNA/DNA ratio presents a potentially faster method for assessing toxicity.
Purpose of the Study:
- To evaluate the RNA/DNA ratio as a sensitive sublethal toxicity endpoint in Caenorhabditis elegans.
- To compare the sensitivity of the RNA/DNA ratio with other sublethal endpoints for metal toxicity.
- To assess the utility of this method for mass screening of toxicants.
Main Methods:
- Exposure of synchronized, prereproductive Caenorhabditis elegans cultures to various metal concentrations (Cu, Pb, Cd, Zn) for 48 hours.
- Measurement of the RNA/DNA ratio as a toxicity endpoint.
- Comparison of RNA/DNA ratio sensitivity with individual growth inhibition after 72-hour exposure.
Main Results:
- The RNA/DNA ratio demonstrated median effective concentration (EC50) values for Cu, Pb, Cd, and Zn (0.05, 0.6, 6.1, and 35 mg/L, respectively).
- This endpoint was slightly more sensitive than the reduction of individual growth after 72-hour exposure.
- The method allows for near-simultaneous assessment of sublethal toxicity in multiple samples.
Conclusions:
- The RNA/DNA ratio is a sensitive and efficient sublethal toxicity endpoint for Caenorhabditis elegans, especially for metal exposure.
- This method facilitates rapid, large-scale screening of environmental toxicants.
- Caenorhabditis elegans exhibits particular sensitivity to copper toxicity when assessed by the RNA/DNA ratio.
