The prevalent use of plastics in contemporary farming has resulted in the abundant occurrence of microplastics and nanoplastics in farmland soils. Scientists at the University of Illinois Urbana-Champaign have sounded the alarm that such plastics may foster the growth of antibiotic-resistant bacteria within our food chain.
Like many other sectors, modern agriculture substantially relies on plastics. Examples include plastic mulch used in vegetable patches, PVC pathways for controlling water runoff, polyethylene barriers in high tunnels, and plastic receptacles for seeds, fertilizers, and herbicides. Recent investigations by the University of Illinois Urbana-Champaign underline that these plastics are now extensively scattered throughout agricultural lands as micro- and nanoplastics.
The presence of microplastics is not exactly a novel discovery; they’ve been detected in virtually all ecosystems and organisms worldwide. However, the twist here, as noted by researchers from the College of Agricultural, Consumer and Environmental Sciences (ACES), is that micro- and nanoplastics in agricultural lands could foster antibiotic-resistant bacteria, providing a potential pathway into our food.
According to Jayashree Nath, a postdoctoral researcher with the Department of Food Science and Human Nutrition at ACES and author of the study, “Plastic may not inherently be highly toxic, but it serves as a medium for transferring disease-causing and antimicrobial-resistant bacteria into the food supply. This issue is relatively unknown, and we aim to raise consciousness about it.”
The connection between microplastics and antibiotic resistance might seem obscure. To explain, plastics have a remarkable ability to adsorb, meaning that chemicals and tiny organisms readily adhere to plastic. Substances like pesticides and heavy metals that would normally pass through soil quickly tend to linger and concentrate upon contact with plastics. Similarly, naturally occurring soil bacteria tend to gather on the stable surfaces of microplastics, leading to the formation of biofilms.
Microplastic pieces, isolated from Illinois farmland, might offer pathogenic bacteria the ideal foundation to develop antibiotic resistance and share related genes with nearby bacteria. A new review paper from the University of Illinois emphasizes the need for further exploration to elucidate the interaction between microplastics and microbes in the areas where our food is cultivated.
When bacteria encounter unfamiliar chemical substances on this new base, they activate stress response genes that inadvertently enable them to resist other chemicals, including antibiotics. Bacteria attaching to the same surface often share these genes through horizontal gene transfer. Nanoplastics, which can infiltrate bacterial cells, present a unique kind of stress, potentially leading to the same result.
“Bacteria have been evolving ways to handle stress for millions of years. Plastic represents a foreign material they have never encountered in nature, prompting them to use these genetic tools to manage the stress,” said Pratik Banerjee, associate professor in FSHN and Illinois Extension specialist and the study’s co-author. “Our study also reveals that bacteria may become both more aggressive and more resistant to antimicrobials in the presence of plastics.”
This type of gene transfer has been observed in environments like water, but it’s still a theoretical concept in agricultural soil. Researchers Nath and Banerjee are conducting laboratory studies to document the process.
“Soil has not been studied extensively in this context,” Banerjee remarked. “We must grasp what is happening in soil, as our suspicion and dread is that the condition could be even more critical than in water.”
He continued, “One technical challenge is that soil is a complex medium to manage when trying to isolate microplastics, unlike water where they can simply be filtered. However, we have made significant progress due to Jayashree and our partnership with the Illinois Sustainable Technology Center.”
The authors underscore that pathogens in food often originate from the soil itself, but nanoplastics and antibiotic-resistant bacteria could penetrate roots and plant tissues, where they cannot be washed away. While nanoplastics have been found in and on crops, this field of study is still emerging, and much remains unknown. Banerjee’s research team intends to explore this question further.
In conclusion, microplastics are unlikely to disappear as they persist in the environment for hundreds of years or more. The authors urge a better understanding of their effects on soil and our food system, increased awareness, and a transition towards biodegradable plastic alternatives.
The study, titled “Interaction of Microbes with Microplastics and Nanoplastics in the Agroecosystems—Impact on Antimicrobial Resistance” by Jayashree Nath, Jayita De, Shantanu Sur, and Pratik Banerjee, was published on 29 June 2023 in Pathogens, with the DOI 10.3390/pathogens12070888, and was financed by the National Institute of Food and Agriculture.
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Frequently Asked Questions (FAQs) about microplastics
What is the main concern regarding microplastics and nanoplastics in agricultural soils?
The main concern is that these plastics, widely dispersed in farmland, may foster the growth of antibiotic-resistant bacteria, posing a threat to our food chain.
How do plastics promote antibiotic resistance in bacteria?
Plastics act as excellent adsorbents, attracting chemicals and microorganisms that love to stick to them. Bacteria form biofilms on these surfaces and may activate genes that help resist chemicals, including antibiotics. Nanoplastics can also enter bacterial cells, causing a stress response that may lead to the same result.
What are some examples of the use of plastics in modern farming?
Modern farming uses plastics in various ways, such as plastic mulch in vegetable beds, PVC channels for water runoff management, polyethylene shields for high tunnels, and plastic containers for seeds, fertilizers, and herbicides.
Is the gene transfer between bacteria on microplastics a proven phenomenon in agricultural soil?
Gene transfer on microplastics has been documented in water environments, but in agricultural soil, the phenomenon is still hypothetical. Current laboratory studies are attempting to document this gene transfer in soil.
What are the potential solutions or steps to mitigate the impact of microplastics on soil and food?
The authors of the study emphasize the need to understand the impacts of microplastics on soil and the food system, raise awareness, and push towards the use of biodegradable plastic alternatives.
More about microplastics
- University of Illinois Urbana-Champaign
- Illinois Sustainable Technology Center
- National Institute of Food and Agriculture
- Pathogens Journal
