Stop Calling Me Edna!

Every day, we leave our mark on every place we go. Skin cells and hairs that fall off of us regularly, waste products that enter our sewage system, and even saliva on half-eaten food will all hold a handful of human cells that bear our unique genetic signature. Thanks to the power of environmental DNA collection, or eDNA, we now know how to collect and read many new clues that have been left behind.

As an ecologist, I see this tool used in many different ways in both my professional and personal life. Since the the name of the tool is constantly changed to Edna by the ever-so-thoughtful spell checker who lives in my texting app, it's pretty clear that the name is not well-known. But the process is everywhere.

eDNA is a bit different than direct DNA sampling. Direct DNA sampling finds a specific object that they know will have DNA, like a strand of hair, and tests it for certain genes. Environmental DNA collects a medium, like water, soil, air and even blood, and filters out all the scraps of living material it can- it then looks for tiny bits of DNA that could have fallen in there

This technology has been around for a while, and its uses are very versatile. It's probably hard to find anyone who hasn't been exposed to this concept in modern entertainment. Forensic crime scene investigations and blood extraction in Jurassic Park are two well-known examples, but the power of this tool has expanded way beyond dead bodies and dinosaurs.

Here are some amazing examples of how scientists have harnessed this tool to do hundreds of different tasks.

Human Health

Medicine is a great example of where DNA testing really began. While direct testing has been a core use of DNA analysis since its inception, the power of harnessing incidental DNA has led to a wide range of creative solutions in several different fields.

Reproductive Medicine

I spent the first three-quarters of 2012 pregnant, with a second, surprise sibling showing up in early 2014. Within that brief window, a fundamental shift happened in neonatal medicine. Checking for potential genetic risks once relied on a combination of ultrasound and amniocentesis, or collecting amniotic fluid to look for fetal cells. I went through this with my first pregnancy. 18 months later, our insurance company had approved a simple blood test that could analyze bits of fetal DNA that had been returned into my bloodstream through the placenta.

The understanding that we can test fetal genes through a mother's blood gave us a lot more non-invasive information. Gender can be typed before a baby has any genitals. Genetic issues can be found early, which has led in some cases to preventative fetal surgeries and early gene splicing.

Epidemiology

To control infectious disease and monitor for outbreaks, regular testing needs to happen. But monitoring the public requires working with a wide range of personalities and personal circumstances. Some people may come in for testing more often than necessary, while others will avoid it due to reasons like personal choice, lack of funds for medical visits, lack of medical leave, lack of symptoms, and no time.

eDNA presents a less intrusive way to monitor for general outbreaks. This is typically done by testing wastewater. In places like universities, testing for conditions like meningitis and measles can provide critical, early information that allows for actions like prevention and quarantines. A good sampling protocol can even catch these diseases in a single dorm before they've spread all over campus.

Public Health officials can also use the same technologies to find which waterfront home has a leaky septic field when fecal e. coli bacteria is identified in a body of water. In other cases, it can also prove that the bacteria doesn't come from humans, but from animals like a herd of cows or a family of raccoons. Some enterprising companies will also use both direct and eDNA samples to tell you the breed of dog who is leaving presents in your yard when you're at work.

Ecology and Wildlife Biology

Wildlife biologists also use eDNA to learn about populations within the natural world. This can be done to get a broad understanding of biodiversity in an area or a targeted look for a certain family, genus, or species. This technology is being regularly used by universities and private scientists, plus federal, state and local agencies.

This technology has been used to look for endangered species that are difficult to find. eDNA sampling can tell you how many distinct population groups of migratory species are in an area. It can be used for regulatory purposes to find habitat that requires protection or identify invasive species.

eDNA sampling can be done by straining a water sample for cells and processing them. It can be done in ponds, throughout stream systems or in the ocean. Water samples for eDNA is also used to find invasive species. On the Pacific Coast, the invasive European Green Crab is a big threat to local shellfish populations. Many local groups are doing periodic monitoring of their estuaries to try and find them when their population is low enough that they can be excluded. In areas where invasive fish, like carp, have taken over a waterway, biologists may go to extreme measures to kill all of them in an area. Afterward, they can sample the water over and over until it's clear that there are no carp left to repopulate the natural waters.

On land, eDNA is mostly used on saliva at feeding stations, or soil sampling along game trails that catch hair, and scat, or animal waste. Solitary mammals like cougars, fishers, and wolverines are difficult to find and count. This gives scientists a way to find different individuals without tagging or harassing them. Broader eDNA sampling protocols can also identify species that are out of their known geographic range, so not expected in an area.

Epidemiologists also work in agricultural and natural ecosystems. Farmers can test the water that runs off the field to look for molds, blights or other diseases that can risk the health of crops. Leaf litter and humus in forests that have lost their leaves can be tested for DNA of likely insect species.

Other Applications

Use of eDNA has made it to a number of different disciplines. This versatile technology requires two ingredients: something to test with sufficiently preserved DNA and a sample to compare it against. From there, you need a specific question that genetic testing can answer and knowledge of where to find the evidence.

This gives eDNA a wide range of potential applications. Soil sampling may answer questions in history, genealogy, paleontology, and archaeology. Rinse water from the inside of an old barrel could be used to inform topics like wine-making, where it can be used to pin down a grape variety no longer used. Reverse engineers can use the science on broths or sauces to try and recreate ingredients and proportions of secret recipes.

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eDNA is an incredibly powerful way to find genetic needles in huge environmental haystacks. Creative professionals will almost certainly continue to use this tool to uncover long-buried answers to hidden or previously unanswerable questions. As this technology offers new, non-invasive ways of answering big questions, it's certain to become more well-known. Perhaps it may someday be so common that the spell-checker in my chat app finally gets it right.

Ednas of the world, beware!