When researchers seek a clear baseline of antibiotic resistance, Antarctica has become the standard choice. There is no intensive farming or overused clinics. There are no pharmacies within several hundred miles of most sites. There was an assumption that remote = clean.
What’s happening on plastic-strewn beaches in the same remote environment begins to complicate that assumption. It’s not about what the plastic is made of. What lives on it?
Fildes Fragment
A team led by researchers from the Autonomous University of Madrid (UAM) walked the shores of two lakes and a protected island on the Fildes Peninsula, near King George Island, with sterile sample bags in hand.
Their three locations were Lake Uruguay, Lake Ionosferico, and Ardley Island, an Antarctic Specially Protected Area.
Plastic was nothing new. Expanded polystyrene and polyurethane foam – the same materials used to pack your luggage back home.
plastic ecosystem
Plastics in water and soil quickly grow a thin film of bacteria. The plasticosphere is a membrane of living organisms that is dense, active, and distinct from the surrounding world.
Bacteria in plastispheres can exchange genes more easily than bacteria floating freely in soil or water. The surface allows them to stick together, colonize nearby, and exchange DNA across species boundaries.
It is already known that marine plastiphia collect antibiotic resistance traits, and the first major paper on this was published from the open ocean. No one was checking the bottom of the world.
Genes clustered on rubble
Juan Manuel Valenzuela Lazaro, a UAM researcher and lead author of the study, conducted a test that can scan for hundreds of resistance genes at once. The team conducted experiments on plastic biofilms, adjacent soil, and lake water.
Across all samples, they found 294 different antibiotic resistance genes and 52 pieces of DNA that help such genes jump between bacteria. Of these, 83 (approximately 28%) appeared only on plastic.
Only two unique genes were produced from the surrounding soil and water. Almost all of the antibiotic resistance the researchers found was on the plastic, with little resistance of its own in the surrounding environment.
High-risk resistance emerges
The researchers classified 294 genes according to how dangerous they pose to human medicine.
Sixteen people fell into the category of most concern, those associated with nosocomial infections and infections that are difficult to treat.
Five of them were found in Ardley Island plastic alone. Prior to this study, the two had never been recorded anywhere in Antarctica. they have it now.
mobile genetic elements
A sharper pattern appeared in the mobile genetic elements themselves, the pieces of DNA that allow resistance traits to jump between unrelated bacteria.
On the plastic, these fragments partnered with antibiotic resistance genes 20 times more frequently than in nearby soil or water. This is the pattern that distinguishes plastic from everything else around it.
The genes that bacteria use to grab and mobilize antibiotic resistance traits (most commonly found in hospital strains) were 16 times more common on plastic than off plastic.
Not only did plastic hold antibiotic resistance; It appears to contain the molecular tools needed to move genes from one bacterium to another.
Live bacteria found
To eliminate genetic remnants that died long ago, the researchers froze the plastic for several months and tried to grow bacteria from it on culture plates mixed with antibiotics.
Seven different strains have returned. Most of them are Pseudomonas genus There are plants that are native to this area and animals that like the cold. Pedobacter.
All of the strains that came back were resistant to at least one antibiotic at a level that doctors were concerned about.
Each also had the genetic machinery to jump resistance to other bacteria. alive. It’s not just frozen traces of something that was once there.
Genes survive in isolation
The research team tested soil and water for five common antibiotics. None exceeded the detection limit. So what keeps these genes alive on plastic when nothing seems to be selected for?
A 2018 study of pristine Antarctic soil linked resistance there to naturally evolved ancient genes that predate human antibiotics.
Other studies have linked it to heavy metals in penguin guano. Plastics seem to collect and concentrate what is already present in the environment.
What does this change?
Until now, the image of Antarctic microbes has been divided into two directions. One is ancient and evolved naturally, or faintly marked by a signal from a research base. The plastic-derived resistance seen here is something different.
Plastic debris not only collects resistance properties. It appears to be combining them with molecular tools that can spread those traits between species, keeping carriers alive through the Antarctic winter.
Recent research had already warned that the continent was unlikely to be immune from antimicrobial resistance.
This work shows where the real hotspots are. For scientists tracking how resistance moves globally, this is a new node on the map, one where bacteria and genes can be sent back to the wider world through migratory birds, ocean currents or expedition traffic.
This study Communication Earth and Environment.
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