Is the presence of microplastics in soil contributing to the growth of antibiotic-resistant bacteria in our food supply?
Researchers from the University of Illinois Urbana-Champaign suggest that this is a genuine concern. Modern agriculture is heavily dependent on plastic materials, ranging from plastic sheets used for mulching to polyethylene covers for tunnels.
The team of scientists highlights that microplastics have become prevalent in farmland soil, potentially providing a pathway for antibiotic-resistant bacteria to enter our food.
These tiny plastic particles can serve as hubs for bacteria, altering their genetic makeup in a way that fosters antibiotic resistance.
Jayashree Nath, a postdoctoral fellow in the Department of Food Science and Human Nutrition, stated, "While plastic itself may not be inherently harmful, it can serve as a carrier for harmful and antibiotic-resistant bacteria into our food system."
The team aims to increase public awareness about this lesser-known issue.
One reason for the concern is that plastics have a high adsorption capacity, making them a magnet for chemicals and microorganisms.
Substances like pesticides and heavy metals, which would typically be flushed through the soil, tend to linger when they come into contact with plastics.
Likewise, soil-dwelling bacteria and microorganisms tend to cluster on the stable surfaces of microplastics, creating biofilms.
When these bacteria are exposed to unfamiliar chemicals on their new plastic homes, they activate stress-response genes, which can inadvertently make them resistant to other chemicals, including antibiotics.
Bacteria residing on the same plastic surface often share these resistance genes through horizontal gene transfer.
Nanoplastics pose a different but equally concerning stress factor for bacteria, leading to similar outcomes.
Pratik Banerjee, an associate professor involved in the study, noted, "Bacteria have developed genetic coping mechanisms over millions of years. Plastics are a novel environmental challenge for them, triggering these ancient genetic responses, which may also increase their resistance to antibiotics."
While the transfer of antibiotic-resistant genes among bacteria on microplastics has been observed in aquatic environments, its occurrence in agricultural soil remains speculative but concerning.
Banerjee added, "Soil is a less-studied component in this research area. We need to focus on understanding soil dynamics because the situation could potentially be more alarming than in aquatic systems."
He also mentioned the technical challenges of studying soil, as it is more complex to isolate microplastics from soil compared to water.