11-Feb-2010 - University of Guelph

Mescal 'worm' test shows DNA leaks into preservatives

Just because you don't swallow the worm at the bottom of a bottle of mescal doesn't mean you have avoided the essential worminess of the potent Mexican liquor, according to scientists at the University of Guelph. Researchers from U of G's Biodiversity Institute of Ontario (BIO) have discovered that mescal itself contains the DNA of the agave butterfly caterpillar — the famously tasty "worm" that many avoid consuming. Their findings will appear in BioTechniques.

The BIO researchers set out to test a hypothesis that DNA from a preserved specimen can leak into its preservative liquid. As part of their study, they tested a sample of liquid from a bottle of mescal. The liquor was found to contain DNA, which they amplified and sequenced to obtain a DNA barcode. Comparing the sample to thousands of records of Lepidoptera DNA barcodes stored in the Barcode of Life Data Systems database at Guelph confirmed that the mescal liquid contained DNA related to the agave's family.

"This is a surprising result," said research team member Mehrdad Hajibabaei, Assistant Professor, BIO and Department of Integrative Biology. He noted that mescal contains only 40 per cent ethanol and potentially many impurities that can degrade DNA.

"Showing that the DNA of a preserved specimen can be obtained from the preservative liquid introduces a range of important possibilities," Hajibabaei said. "We can develop inexpensive, high-throughput, field-friendly and non-invasive genetic analysis protocols for situations where the original tissue cannot be touched or when there is simply no sample left for analysis."

The scientists also successfully identified other "fresh" specimens contained in preservative ethanol — including whole insects (caddisflies and mayflies) and plant leaves — as well as seven preserved specimens collected seven to 10 years earlier.

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