Biological control measure for zebra mussels proposed by University of Lethbridge research team shows promise

By Tim Kalinowski

New research at the University of Lethbridge may well help stave off one of southern Alberta agriculture’s most pressing future problems.

For years irrigation districts in the region have been on high alert when it comes to zebra or quagga mussels. Sniffer dogs, boat inspection stations and recreational access closures have all been employed at times to help prevent this creature from establishing itself and wreaking havoc on local farm irrigation infrastructure and water supply pipes. But the prevailing thought among researchers looking at the question is one day all these security walls and levels of prevention will be breached.

If that were to happen, there needs to be Plan B: A way to kill off the mussels without causing longterm environmental damage.

Student researchers on the university’s iGem team, which recently won a gold medal for their findings on the subject at the 2018 International Genetically Engineered Machine (iGEM) competition in Boston, MA,  may have found a way to walk this precarious path by using encapsulin P-22 nanocompartments. Nanocompartments are spherical bacterial organelle-like compartments, (derived from non-replicating aspects of bacteria), which are designed to encapsulate one type of protein or toxin, in this case, and take them directly into the cells of a target organism using genetic encoding. In essence, creating a biological counter-measure coded to kill one specific organism by the researchers doing the programming.

“Targeting specific tissues, cell types, or cellular organelles is important for the correct treatment of many diseases,” says the iGem press release announcing the gold medal win. “The U of L team created software that would help others overcome these problems. The team members also demonstrated how they can successfully encapsulate cargo within P22 “nanocompartments” that can target zebra and quagga mussels with species-specific toxins.”

While the simulation models are promising, a challenge for researchers is to test these models in southern Alberta without bringing in live samples of zebra mussels, whose microscopic offspring can contaminate local water and irrigation systems without being seen.

“The only ethical hurdle that I see is the fact you won’t have to bring zebra mussels into an area where there are no zebra mussels,” confirms Dr. Hans-Joachim Weiden, who leads the iGem program at the University of Lethbridge. “So you have to go somewhere else to test it where there are zebra mussels already.”

Weiden is also cognizant of the fact that if a researcher can program a nanocompartment to carry a toxin into the cells of one type of species, the prospect of doing so for any species also exists. That is why nanocompartment researchers must follow strict guidelines, he says.

“You are putting a toxin in which is specific for zebra mussels and quagga mussels that has been used in the past in the Great Lakes, for instance, to control that,” he explains. “That’s a natural toxin which is selective for that kind of group. That is why we are not inventing anything new— we are using that toxin.

“The existing commercial product (Zequanox) uses a bacterial strain which actually expresses (the toxin), and that is going to be put in the lake. We are trying (in our research) to get rid of the bacterial chassis, and do everything in lab so we have full control over it, which is exactly why this is a superior solution (to Zequanox).”

“Because our students have control over the potency of the product,” he adds, “there will be no blanket application for that.”

Nanocompartments are derived from bacteria, but do not have any self-replication genes expressed, he says, so if released into nature will only target and kill the organism they are programmed to go after, and only remain active for a short period of time after being released.

“There is no potential for it to be off target,” says Weiden. “Evolution has taken care of that already (by creating a natural toxin for the mussels). The delivery device we have is clearly non-replicable; so it is safe as any product in the marketplace.”