Jun 3 2008
Earthworms are proving to be great detectives when it comes to identifying what pollutants are present in our soils. They are helping scientists to build up a detailed picture of how toxic chemicals and metals in soils interact with living organisms, by demonstrating the effects these toxins have on their genes.
Researchers from Cardiff and Edinburgh Universities, Imperial College London and the Centre for Ecology & Hydrology (CEH) used a systems toxicology approach to understand the impact of four contaminants on the earthworms (Lumbricus rubellus). Their findings are published today in two complementary research papers in BioMed Central’s open access journals BMC Biology and BMC Genomics.
Dr Peter Kille from Cardiff University led the research team. He said, ‘The earthworm is widely used as a model organism for soil testing but standard laboratory tests do not reveal how pollutants behave in the genomic system, and how the system adapts to deal with it. Although the earthworm genome has not been sequenced, we’ve been able to create a comprehensive expressed sequence tag dataset, that enables the development of tools that bring the earthworm into the genomics arena, and makes it the soil pollution equivalent of a canary in a coalmine.’
Using a new 8,000-element gene microarray (an analysis system that allows the measurement of thousands of genes using a single sample) the researchers tested the effects of copper, cadmium, the poly-aromatic hydrocarbon fluoroanthene, and the agrochemical atrazine.
The tests revealed subtle changes, induced by the toxins, in the worms’ gene expression patterns. The effects of copper exposure, in particular, identified genetic and metabolic changes as well as massive deterioration in the worms’ physical health.
Dr Kille said, ‘The research helps us to understand how, over millions of years, the earthworm has evolved adaptive mechanisms for dealing with soil pollution through genetically programmed responses. It also provides important clues to how humans will react or adapt to chemical exposure, as we share some common gene pathways with earthworms.’
This multidisciplinary research combined the systems toxicology approach with technologies usually used in isolation. The result is a powerful tool for understanding how ecologically important organisms like the earthworm respond to contaminants and also opens up the possibility of new, more effective, soil monitoring and bioremediation strategies.
The research was funded by the Natural Environment Research Council through its Environmental Genomics thematic programme.