The bugs in your teabag counted with eDNA

Commercial tea leaves contain traces of arthropod DNA, according to a study published in Biology Letters.

Aside from establishing that yes, there are insect traces in your teabag, the research demonstrates a nifty new technique: the ability to extract eDNA from dried plants.

Environmental DNA, or eDNA, is a method of finding DNA fragments left behind by many different species in a given environment – like seawater or river water. It can be used to identify traces of hundreds of different species, without ever seeing the creatures themselves.

Typically, it works best with water. But this team of researchers, who are based at Trier University and the Max Planck Institute for Evolutionary Biology, both in Germany, have figured out a method for getting eDNA from dried leaves.

“You usually wash off eDNA and filter the DNA-containing particles out of the wash,” says lead author Dr Henrik Krehenwinkel, a junior professor at Trier University.

“We extracted DNA directly from homogenised plant material. So we extracted DNA from the plant and associated eDNA at the same time.

“The difficulty here is that we need to enrich the arthropod DNA from the plant DNA. That can be done with the new assay we developed.”

More on eDNA: Cosmos 90’s feature, Something in the water

What better way to demonstrate the method works than examining teabags?

The researchers extracted DNA from several dozen different commercially bought teabags and dried herbs, including chamomile, mint, tea and parsley.

They were able to spot over 1,000 different species of arthropod from the eDNA they found.

Because they were specifically looking for arthropods, the researchers don’t know if there are traces of other organisms present in the tea: eDNA can only show you what you’re looking for.

“We are now checking if the DNA of microbial populations associated with the tea plant is also preserved in the teabag,” says Krehenwinkel.

“Also, we are thinking about comparing regular and organic teas for differences in the recovered diversity of arthropods.”

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