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Contaminated water: find the source by DNA


Professor at the Armand-Frappier Health Biotechnology Center of the National Institute for Scientific Research (INRS), Richard Villemur has been working for twenty years on strategies for detecting animal contamination in water by faecal excretion.

It uses mitochondrial DNA, a circular DNA molecule found in all living things.

Mr. Villemur recently published the results of his latest research work in collaboration with doctoral student Rose Ragot in the scientific journal Environmental Monitoring and Assessment.

With the help of databases, they designed genetic primers to recognize the majority of mammals and birds, as well as many amphibians and fish. These primers are small DNA sequences that upon analysis stop at DNA that is unique to an organism in a sample, explains Villemur.

Thanks to PCR technology, the same one used for COVID-19 screening tests, this portion of the DNA is amplified in a way astronomical to determine which species may be present.

Four rivers studied

The method designed by the professor considers several animals at the same time, thus avoiding carrying out multiple PCR analyses.

Ms. Ragot, a biology student, was able to show the effectiveness of the approach with water samples from four rivers flowing in particular near agricultural areas.

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Mr. Villemur mentions that the bacterial indicators (such as coliforms) currently used to detect the presence of fecal contamination do not make it possible to determine the source of the problem, unlike mitochondrial DNA.

The tool I developed would allow to discover which animal is the cause of faecal contamination or to make strong hypotheses about it. Watershed managers could knock on the right doors […] and take remedial actions to prevent contamination from returning on a regular basishe said in an interview with The Canadian Press.

Possible sources of pollution

According to him, the approach could be useful in regions where human and agricultural activities intersect while the possible sources of pollution are multiple: overflows, problematic septic tanks or a defective water treatment plant, for example.

He mentions that the presence of bovine material in a river can come from the consumption of meat by humans and thus signal a problem in the treatment of wastewater.

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Mr. Villemur would like his method to be deployed in the field using an instrument that would give results almost in real time.

It would require having partners who would be interested in moving forward with the application of the technologyhe says.

Better control of the environment

The professor believes that the method can also be used to follow the evolution of the animal profile in the rivers.

This observation could take place at the same time as the taking of samples to measure the level of coliforms, evokes Mr. Villemur.

Watershed managers could then establish a correlation between the detection of faecal contamination and the presence of certain species, in particular invasive species, in greater numbers compared to others, he explains.

It is a management and monitoring tool that could lead us to better control of the environmentsays Mr. Villemur.

He points out that new research addressing this avenue is forthcoming. Mrs. Ragot and he examined nearly a hundred samples from about thirty river points.

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