A researcher's keen eye and spirit of curiosity led to the discovery of a new method for cell engineering - a finding that opens doors to more sustainable sources for everything from fuel to vitamin supplements.
Western graduate Emma Walker, PhD'25, uncovered a more effective way to deliver DNA into diatoms, single-celled algae found near the surface of oceans, lakes and rivers. Diatoms, which store energy in the form of natural oils, could offer a cheaper, cleaner way to develop biofuels and nutraceuticals such as omega-3 fatty acids, antioxidants and vitamins.
But it's Walker's approach that lays the foundation to embrace those possibilities.
"People have long been interested in genetically modifying diatoms to make medicines, biofuels and other valuable compounds," said the former PhD candidate.
The study, led by Walker and Schulich School of Medicine & Dentistry professor Bogumil Karas, was published in Nature Communications and details a way to deliver DNA and gene-editing tools into diatoms.
Reliable DNA delivery is the key step that will allow researchers to rapidly engineer cells to produce food, medicines and fuels.
"I started the synthetic diatom project to develop tools that enable the delivery or replacement of individual genes, allowing us to understand their function and selectively redesign genetic components when needed," said Karas.
Delivering that DNA was one of the major bottlenecks.
Diatoms are encased in a frustule, a protective shell made of silica, to help them survive in nature. However, this protective casing can make genetic engineering slow, inconsistent and often unreliable in the lab.
"It was a bit serendipitous. I was testing a method to deliver DNA through electroporation - where we electrocute cells to create temporary pores that allow the insertion of molecules into a cell - and three tiny colonies had emerged, which was exciting," said Walker. "When Professor Karas repeated this experiment, he had more than a hundred colonies, so I wanted to see why his experiment was more efficient than mine because, to me, it's not random luck."
She worked backwards to test different conditions while repeating the experiment. After a couple weeks of trialing, she realized the cells Karas used were older. When these old cells were viewed under the microscope, some had taken on a characteristic spherical shape that suggested the outer cell wall was breaking down. Walker hypothesized that degradation of the diatom cell wall was influencing the ability to insert new molecules. She tested her hypothesis by treating the diatom cells with a bit of alcalase, an enzyme that can poke holes in the cell wall.
This drastically improved her ability to move molecules into the diatom through electroporation - so much so, that she was now generating upwards of 20,000 colonies in a single experiment.
It was an important breakthrough, because it enabled the researchers to begin testing the newfound limits of their method to insert new molecules - key to redesigning diatoms to produce compounds that would increase their potential for creating biofuels and health foods.
"This widens our ability to engineer the organism, which is important because one day we want to be able to create a strain of this diatom that is controlled by a synthetically built genome. To do that, we need to be able to engineer this organism easily and quickly," said Walker.
The study also showed a low-cost chemical method for inserting molecules using polyethylene glycol (PEG) worked better once the cell wall was removed, making this approach more accessible as labs would not need to rely on expensive electroporation equipment.
Researchers also discovered that diatoms are capable of assembling large pieces of DNA inside their own cells.
"Suddenly, we could deliver very large pieces of DNA, not just small fragments." - Emma Walker, PhD'25
This new approach could dramatically speed up research timelines, Karas said.
"Instead of spending up to few weeks moving DNA through bacteria before it reaches a diatom, we can now introduce the synthetic DNA directly," said Karas. "This saves a lot of time, a lot of effort, reduces errors and opens up new possibilities."
These techniques have already been adapted for another diatom species through international collaboration with Dr. Thomas Mock at the University of East Anglia (UK). This brings scientists closer to resynthesizing DNA that can be used to develop greener energy technologies and new health solutions.
"Sometimes the biggest advances come from noticing something unexpected and asking why," said Walker.
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