Earthworms as the ultimate strategy to face microplastic pollution

Have you ever seen an earthworm make magic? These little creatures can, for instance, eat leaves and make them disappear! Earthworms are one of the few animals capable of decomposing organic material. So, even though they seem insignificant living things, it is hard to imagine a world without them. But, what if I told you earthworms could also make microplastics in soil vanish? What if they represent the ultimate strategy to face microplastic pollution?

I am Mireia Pagès Guitart, a Catalan biomedical scientist, a second-year student of the Master’s Programme in Pharmaceutical Research, Development and Safety at the University of Helsinki, and a new HiLIFE trainee! With the support of the HiLIFE Research Trainee Scholarship, my ambition was to engage in applying sustainability to science, a much-needed climate action.

Even though my passion has always relied on combining both topics (sustainable science), this dream didn’t come true until I came upon Prof. Michael Jeltsch. He is another scientist fond of practicing sustainability, both in his lab and his research projects. What amazed me the most was the earthworm project that his lab team wanted to carry out: using earthworms as a microplastic degradation strategy.

Earthworm’s digestive system and microbiota

Before joining the group’s lab work, I did an extensive literature review on the earthworms’ digestive system and microbiota. This was useful to expand my background knowledge and have some insights on how to conduct the experimental part of the project.

Earthworm’s digestive system is mainly composed of the gizzard. The gizzard is an amazing structure responsible for grinding and crushing the food. Different digestive glands are also present and contribute to the digestion process by releasing proteolytic enzymes. In other words, these enzymes break down the ingested food into even smaller pieces.

Inside the earthworm’s gut, there is also the microbiota: a community of bacteria. The microbiota maintains the intestinal homeostasis and, most importantly, breaks down carbohydrates that the glands can’t digest, contributing to the digestion process further.

Surprisingly, it has been seen that the earthworms’ digestive system and its microbiota digest contaminants from the ground along organic material. Could this mean that earthworms would be able to turn microplastics into soil fertilizer? Indeed, this would be a promising approach to explore.

Microplastic degradation potential

On my first day in the laboratory, we designed the experimental plan. To make our dreams come true (creating microplastic-degrading earthworms), we should exploit the earthworm’s digestive system properties. For instance, if specific enzymes released by their glands are more effective than others, we could enhance their expression to improve the digestion process.

Overall, it was clear that we would need to modify the earthworm’s DNA to make them transgenic animals. Let’s imagine that we aim to enhance the expression of a certain enzyme. We would take the gene coding for such an enzyme, assemble it in a plasmid (=DNA) and place this plasmid inside a virus. This is known as a cloning step. Next, we would transfer the plasmid inside the earthworm by infecting the animal with the virus. Once inside, the earthworm would express the gene and activate the enzyme production. Finally, we would assess if the microplastics’ degradation takes place.

The beginning of my research

Of course, every experiment needs a control before anything happens. For this reason, since I started my traineeship, I have made the mentioned cloning step with GFP protein instead of any enzyme gene (previous example). GFP protein is easy to detect on animals because it expresses green fluorescence. Using GFP will be useful for us to know if our experimental method on earthworms works at all: earthworms will emit green fluorescence if we are successful. If we are on the right track, we will be able to proceed with the rest of the project afterwards.

During this time, I have also got to know the lab team members and how they work. I give lots of importance to team building, so I am happy to feel that comfortable in this group. I have high expectations for all that I will learn, the lab techniques I will use and the skills I will earn. This traineeship will help me grow both as a scientist and as a person. And, if this project raises meaningful outcomes, we would have a powerful tool to fight one of the biggest issues that we are facing nowadays:  microplastics pollution. 

Studying in Finland is a worthwhile adventure. The snow gives light in the darkest times and the sun is much more appreciated than anywhere else. Also, the University of Helsinki provides plenty of opportunities to keep learning in the best way. All in all, it is an unforgettable experience. You will hear more about my traineeship experience and the research progress later this spring. Keep an eye out because there is more to come!