Moths, on today's menu: plastic mixture

Using models that analyze terrestrial and aquatic environmental pollution, a team led by the PhD student Juliana Ruiz Barrionuevo is researching the plastic biodegradation carried out by the larvae of these insects, as well as the impact of such consumption on the gut microbiota.

Commonly known as "wax moths," their true names are Galleria mellonella and Achroia grisella. However, the truly significant aspect is the ecological role fulfilled by their larvae, linked to their remarkable plastic-eating capacity – that is, their ability to consume and biodegrade different types of plastic.

The fact remains that global pollution from this plastic waste is, at the very least, concerning: over 65 years – from the 1950s to 2015 – a staggering 6.3 billion tons of plastic waste was generated. Therefore, this situation demands immediate action. It is imperative to develop technologies that can mitigate this impact on the environment.

This is where the scientific protagonist of this story, Juliana Ruiz Barrionuevo, comes into play. Together with experts from the Institute of Regional Ecology (IER, CONICET-UNT), and thanks to various overseas specializations, she seeks to uncover more about the potential of these insects, which could hold value in providing a solution to the plastic pollution generated worldwide. Not only that: they aim to unveil how diet fluctuations affect them, considering the consumption of a variety of these materials. This aspect also allows for drawing parallels with the human organism. During the food packaging process or transportation – a stage when they are subjected to temperature changes, for instance – microplastic particles can be released, indirectly affecting human health.


The endogastric system is also an ecosystem.

Barrionuevo and the other professionals at the IER utilize models that analyze terrestrial and aquatic environmental pollution to study plastic consumption by the larvae of these two moths, and how this process affects the insects' gut microbiota. Building upon this premise, the multidisciplinary research team's objective is to understand how the gut bacteria of both insects work to degrade certain plastics, such as polyethylene and polypropylene, within the gut.

This journey began for the fellow with a stay in Puerto Rico in 2022, where she aimed to explore the genetic potential of Galleria mellonella's microbiota. She exposed the larvae to various types of plastics to observe their metabolic response. She was able to do this through a scholarship from the Biotechnology Program for Latin America and the Caribbean, offered by the United Nations University (UNU-BIOLAC). Recently, she was selected for a Fulbright scholarship, which will allow her to return to Puerto Rico and advance with the analyses involving metabolites (substances produced during metabolism, digestion, or other bodily chemical processes).


Preliminary Results and Potential Benefits

Monmany, the director of Barrionuevo and an associate researcher at the IER, explains that both moths exclusively inhabit beehives. The team discovered that, in addition to feeding on beeswax, their diet includes unconventional items like silage bags. "We were interested in understanding how they manage to consume this and whether they truly derive energy from such an unusual source," she notes, acknowledging that their ability to feed on beeswax served as a precedent due to its composition and physical structure being similar to that of plastics.

Furthermore, she shares that Barrionuevo is conducting various experiments to analyze these consumption habits. "The most intriguing aspect is that we are beginning to observe how the microbiotic communities residing in the moths' intestines change with different plastic and other material-based diets," she adds, explaining that this allows them to observe the alterations that occur within the bacterial communities of the intestines.

Through this process, they identified various types of organisms. Some cannot survive and vanish, while others can and become dominant. Additionally, they have results indicating functional modifications that are linked to insect responses based on the consumption of different materials.

These studies can be used to draw parallels with humans who, as mentioned earlier, can ingest tiny particles from packaged foods. In this regard, Monmany clarifies that what occurs in the endogastric system of insects can be replicated in humans, explaining the role that microbiotic communities play in the human intestinal tract. "We must exercise caution because much of our food is packaged, and in such cases, chemicals can be released. These additives are incorporated into plastics to confer malleability or transparency," notes the IER researcher. These chemicals, when released, can adhere to food under certain high or low-temperature conditions. "This disrupts our intestinal microbiota, something very similar to what we are studying with the larvae," she emphasizes.


What's Ahead

With access to the Fulbright scholarship and the upcoming stay in Puerto Rico, Barrionuevo will be able to conduct shotgun sequencing of microorganisms. This method will essentially reveal all the genes present in the digestive tract of G. mellonella and provide insight into how plastic consumption affects larval metabolism. Monmany illustrates this with polyethylene, explaining how it could significantly impact energy reserves accumulation in moths… which could lead to winter mortality.

On the other hand, the experts agree that these studies might not be conducted if we weren't living in a context of high plastic pollution across various ecosystems. They assert that the endogastric system (for vertebrates) is considered by specialists as another type of environment that can be similarly affected by this situation. "We treat ecosystems within living organisms just like we do terrestrial or aquatic ecosystems. They are all analytically similar," states Monmany.

There's a crucial point, emphasized by the scientists: the moths' "abilities" to degrade plastics are not a solution to the global pollution problem. "A fundamental change is urgently needed, both in terms of plastic production and in terms of raising awareness about our purchases and recycling practices," warns the researcher. "The real solution to the problem involves transitioning from a linear economy to a circular one, and this shift should involve not only individuals but also companies and sectors with political influence."



Key Considerations

From the 1950s until 2015, approximately 8.3 billion tons of virgin plastics were generated globally, with 60% of this production occurring after the year 2000. Out of this total, 6.3 billion tons now exist as plastic waste, with a concerning final disposition: only 9% was recycled, 12% was incinerated, while the remaining 79% accumulates in landfills or the environment.

These waste materials are scattered across the globe, originating primarily on continents – many of which are subsequently transported by rivers to reach the oceans, where they form permanent clusters of debris known as "plastic islands." The ecological consequences are more pronounced in aquatic ecosystems than on land. In fact, the majority of recorded species affected by plastic pollution are marine species. Additionally, nanoplastics, in their tiny particles, pose an even greater potential threat, as they are believed to be capable of infiltrating tissues within organisms.


Cite: Conicet NOASUR