Hitchhiker’s Guide to the Plastisphere: exploring the role of microplastics in supporting antimicrobial resistant pathogens

Posted on November 22, 2024   by Emily May Stevenson

Emily May Stevenson takes us behind the scenes of their latest publication 'Selective colonization of microplastics, wood and glass by antimicrobial-resistant and pathogenic bacteria' published in Microbiology.

Plastic pollution is one of the most pressing environmental challenges of our time, but there's more to the story than meets the eye. Beneath the surface of the ocean, rivers and even our soil, plastic debris—particularly microplastics—can act as a haven for harmful bacteria. These microscopic particles don’t just disrupt ecosystems; they may also play a significant role in the global issue of antimicrobial resistance (AMR).

As part of my PhD research at the University of Exeter and Plymouth Marine Laboratory, UK, I’m investigating how microplastics interact with bacterial communities. Our focus is on the "Plastisphere"—a unique ecosystem where microbes attach themselves to plastic debris. These communities can differ significantly from the surrounding environment, and in some cases, they might harbour disease-causing bacteria, including those resistant to antibiotics.

Why does this matter?

Antimicrobial resistance is a growing global health threat. When bacteria become resistant to drugs like antibiotics, it becomes much harder to treat infections in humans and animals. If plastic particles in our environment provide a platform for the growth of drug-resistant bacteria, it could accelerate the spread of AMR, posing serious risks to public health. 

Our research suggests that the type of material—whether it’s plastic or organic—plays a critical role in how bacteria colonise these surfaces. In our latest study, we compared the colonisation of three types of microplastics (polystyrene, nurdles, and bio-beads) with natural substrates like wood and inert materials like glass. Surprisingly, we found that certain plastics, like polystyrene, and even natural materials like wood, significantly enriched antimicrobial-resistant bacteria. Meanwhile, sewage-sourced bio-beads were found to harbour pathogenic Escherichia coli (ExPEC), a bacteria responsible for extra-intestinal infections.

One of the most intriguing findings from our study was that the surface roughness of these particles didn’t significantly influence bacterial colonisation. This challenges the common assumption that rougher surfaces inherently support more bacteria. Instead, it appears that the material itself, rather than its texture, determines the extent to which bacteria can thrive.

Where it all began

This research builds on my master’s project at the University of Exeter, UK, where we began noticing patterns in how different substrates affected bacterial growth. My interest in bio-beads, tiny plastic pellets used in wastewater treatment, was a key motivation for continuing this research. Having seen firsthand the abundance of these beads in the environment, I wanted to explore their potential role in spreading AMR pathogens.

But this project didn’t unfold overnight. What started as a small-scale experiment grew into what we affectionately call the "colossal experiment," with new questions emerging at every turn. Collaborating with an incredible team, we expanded the scope of our research, and it was especially exciting to include findings from my first master’s student, Owen, marking an important milestone in his research career.

The bigger picture

So, what’s the endgame? Ideally, this research will improve our understanding of how microplastics contribute to the evolution and spread of AMR. This knowledge could inform policies on waste management, push for better monitoring of microplastics and AMR in wastewater systems, and ultimately influence risk assessments that guide environmental protection efforts. By identifying the types of particles most likely to support harmful bacterial communities, we can recommend targeted interventions that limit the risks they pose to human, animal, and environmental health.

Looking ahead

We’re only scratching the surface of what’s possible in this field. In fact, our team has already begun several follow-up studies to further investigate how the Plastisphere enriches AMR bacteria and the role microplastics might play in transporting these bacteria through the food chain. These findings could have broad implications, from improving food safety to informing environmental regulations aimed at reducing plastic pollution.

The future of this research is exciting because it has the potential to address critical challenges at the intersection of public health, environmental science, and policy. The more we understand about the hidden dynamics of the Plastisphere, the better equipped we will be to tackle both plastic pollution and the looming threat of antimicrobial resistance.