PCR Technology to Help Find and Fight Invasive ​Mussels

The pristine waters of Flathead Lake that have supported local residents' way of life for centuries are being threatened by invasive species that have devastated lakes and waterways across the country.

The arrival of the first documented zebra and quagga mussels in Montana could mark the beginning of the end for the crown of the continent's signature landscape, according to experts at the Flathead Lake Biological Station (FLBS).

Freshwater mussel genus lampsilis, Source: Wikimedia Commons

These invasive species have infested lakes in almost every state in the U.S., corrupting indigenous ecosystems, clogging drainage and irrigation systems and crashing the economical and recreational value of beaches and harbors.

Dr. Cody Youngbull, one of the station's lead physicists, called the mussels the No. 1 threat currently facing the lake.

However, thanks to a new device that was invented, designed and manufactured by Youngbull and his team, hope is now emerging in the fight to keep the mussels from invading one of the nation's last strongholds.

The team's groundbreaking research in the field of environmental DNA (eDNA) has produced the first digital PCR, or DNA-detecting, device of its kind.

Every living thing produces DNA, and by taking water samples and screening them for certain types of DNA, Youngbull and his team can now determine whether a species is present or not without ever having to see it.

The PCR, or polymerase chain reaction, device can not only detect, but also measure the presence of minute traces of specific kinds of DNA, such as zebra or quagga mussels, in water samples.

PCR technology in itself is nothing new, according to Youngbull. The technology first won a Nobel Prize in the 1980s, and scientists across the globe now utilize it for different purposes. However, the systems used to implement the technology to date have required four different bulky devices that take up enough space to fill a buffet table and cost upward of $200,000, according to Youngbull.

What is revolutionary about the FLBS team's device is the miniaturization of the devices, making the whole system compact enough to fit on a board the size of a laptop and capable of being transported in a backpack.

This improvement will allow researchers to take the device into the field, taking and testing samples on-site to produce results in as little as an hour.

The device works by collecting two-liter water samples from one area of the lake. Those samples are then filtered to remove any debris and added to a control substance, or primer, that allows the device to look for a specific type of DNA by matching it to a sample, or template, of that same kind of DNA.

The filtered water gets sucked into the machine through small tubes comparable in diameter to that of pencil lead. Those tubes carry the water, which is then separated into thousands of individual droplets, only .8 nanoliters each, through the device which looks for the presence of the desired DNA by comparing it to a template.

Each droplet either contains that DNA or does not. The droplets that contain DNA are counted as ones and those that do not contain DNA are counted as zeros.

The system then counts the number of ones to determine the quantity of DNA in each sample and prints out the results.

The entire process takes about 50 minutes to produce results, and, when taken out into the field, can be repeated several times over the course of one day.

Read full article: San Francusco Chronicle

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