Three bacteria that cannot eat plastic alone learned to do it as a team

Research by the Helmholtz Centre for Environmental Research, Leipzig. Published in Frontiers in Microbiology, March 2026.

The biofilm was not supposed to be there. Clinging to the polyurethane tubing of a bioreactor at the Helmholtz Centre for Environmental Research in Leipzig, it was the kind of unwanted growth that laboratories typically scrub away. But Dr. Christian Eberlein and his colleagues saw an opportunity instead of a nuisance. Whatever was growing in that tubing had been surviving on plastic, and it was worth a closer look.

What they found, after scraping off a sample and coaxing it through rounds of culture, was a stable community of three bacterial species that can devour phthalate ester plasticizers - toxic additives found in building materials, food packaging, and personal care products that have been linked to hormonal disruption, metabolic disorders, and certain cancers. No individual member of the trio can digest these compounds alone. Together, they break them down completely. The results appear in Frontiers in Microbiology.

The three partners and their division of labor

DNA sequencing identified the consortium's members: one species from the Pseudomonas putida group, one from the Pseudomonas fluorescens group, and an uncharacterized species of Microbacterium. Grown individually on diethyl phthalate (DEP), a standard model compound for phthalate research, none of the three could use it as a carbon or energy source. They simply sat there, starving in a bath of food they could not eat.

Mixed together, the picture changed dramatically. The consortium could tolerate DEP concentrations up to 888 milligrams per liter and, at 30 degrees Celsius, completely consumed the compound within 24 hours. Further tests showed this teamwork extended beyond DEP to dimethyl phthalate, dipropyl phthalate, and dibutyl phthalate - all common phthalate plasticizers found in contaminated environments.

Cross-feeding: the metabolic handoff

The mechanism is a phenomenon called cross-feeding, where one microbe's metabolic waste becomes another's food. It is a fundamental feature of natural microbial communities - gut bacteria do it constantly - but it had never before been documented in plastic-degrading microbes.

In this consortium, the degradation proceeds through a relay. One species partially breaks down the diethyl phthalate, releasing monoethyl phthalate as an intermediate. Another species picks up that intermediate and cleaves it further into phthalate. The third species may handle subsequent degradation steps. Each organism contributes enzymatic capabilities the others lack, creating a complete degradation pathway that no single species possesses.

Proteomic analysis - cataloguing the proteins each species produces - revealed that the enzymes responsible for the key degradation steps are new to science. They have not been characterized in any previously studied organism. This suggests the consortium represents an independent evolutionary solution to phthalate degradation, not a reshuffling of known biochemical parts.

Evolution on a plastic timeline

Where did these capabilities come from? Eberlein offers a plausible scenario. The initial enzymatic reactions likely co-opted pre-existing enzymes that originally evolved to break down natural molecules containing ester bonds - plenty of these exist in soil and plant material. Phthalate esters, which have been present in the environment at significant concentrations only since the mid-twentieth century, then created selective pressure for more specialized variants.

Seventy-odd years of persistent contamination may not sound like much evolutionary time, but bacteria reproduce fast and swap genes freely. The fact that the consortium was found growing in laboratory tubing - an artificial environment that has existed for a far shorter period - suggests these organisms can adapt to new plastic substrates relatively quickly.

The cross-feeding strategy itself may have evolved because phthalate degradation is biochemically expensive. Breaking the ester bonds requires enzymes that individual species may not produce efficiently or in the right sequence. By distributing the metabolic workload across three partners, each species invests fewer resources while the community as a whole achieves complete degradation.

Phthalates but not polyethylene

A critical limitation deserves plain statement: phthalate esters are plasticizers - additives mixed into plastics to make them flexible - not the structural polymers themselves. The consortium digests the additives, not the plastic backbone. It cannot touch polyethylene, polypropylene, or the other high-volume polymers that constitute the bulk of plastic pollution. Those materials contain highly resistant carbon-carbon bonds that are inaccessible to the enzymes these bacteria deploy.

This matters because phthalates, while genuinely toxic and environmentally concerning, represent a different class of problem than the floating garbage patches in the ocean or the microplastic particles in drinking water. The consortium addresses plasticizer contamination specifically - a meaningful environmental target, but not a solution to plastic waste broadly.

The current work was also conducted under controlled laboratory conditions at a comfortable 30 degrees Celsius, with DEP supplied as the sole carbon source in defined growth medium. Natural environments - wastewater streams, contaminated soils, river sediments - present the consortium with competing microbial communities, fluctuating temperatures, varying pH, and complex mixtures of organic compounds. Whether the trio can maintain its cooperative degradation capacity under those conditions is an open question.

From bioreactor tubing to wastewater treatment

The research team, which participates in the Helmholtz Sustainability Challenge project FINEST (aimed at engineering solutions for a circular economy), has a clear next target. Dr. Hermann Heipieper, the study's senior author, plans to test the consortium in actual wastewater samples containing microplastics to see whether it can remove phthalate contamination under realistic conditions.

Beyond that, the concept of bioaugmentation - introducing specialized microbes into polluted environments to accelerate contaminant breakdown - could leverage this consortium's capabilities. Phthalate-contaminated sites include industrial wastewater outflows, landfill leachate, and agricultural soils where plastic mulch films have degraded. If the consortium functions in these settings, it could offer a biological complement to physical and chemical remediation methods.

The broader lesson may be about where to look for plastic-degrading organisms. Hundreds of individual plastic-eating microbes have been identified over the past 25 years, but most work slowly, require high temperatures, and function only in controlled bioreactors. This study suggests that the real action may lie in microbial communities rather than individual superstars - and that the bioreactor's own plumbing is not a bad place to start searching.