Our world is in the midst of a plastic waste crisis. It is estimated that over 8.3 billion tons of plastic have been produced since the 1950s, and only about 9% of it has been recycled. The rest has ended up in landfills or in our environment, including the oceans, where it is causing severe damage to marine ecosystems. This plastic waste, which does not biodegrade, is expected to persist in the environment for hundreds or even thousands of years. Given the significant environmental impact and the difficulty of dealing with this waste, novel solutions are desperately needed.
One of these potential solutions lies in the world of microbiology, with the discovery and engineering of plastic-eating bacteria.
A Deep Dive into Plastic-Eating Bacteria
Bacteria have adapted over billions of years to survive in diverse environments, including those inundated with plastic waste. In recent years, scientists have identified several bacteria species that can consume or "eat" different plastic types.
In 2016, a bacterium, Ideonella sakaiensis, capable of breaking down polyethylene terephthalate (PET)—a widespread plastic used in bottles and clothing—was discovered in a Japanese waste dump. This bacterium secretes PETase and MHETase enzymes that decompose PET into basic building blocks, which the bacteria then use as a food source.
However, a significant advancement came from the Royal Netherlands Institute for Sea Research (NIOZ), where researchers demonstrated that Rhodococcus ruber, a bacterium, can actually digest plastic.
The Workings of Rhodococcus Ruber
The NIOZ experiments carried out by PhD student Maaike Goudriaan employed a unique plastic variant incorporating a distinct form of carbon, 13C, for the laboratory tests. This special plastic, after being treated with UV light to emulate sunlight's effect on breaking down plastic into manageable portions for bacteria, was exposed to Rhodococcus ruber in artificial seawater. The researchers noticed the carbon-13 form being released as CO2 above the water, indicating the plastic's breakdown.
This marks the first instance where it was conclusively shown that bacteria can metabolize plastic into CO2 and other benign molecules. Goudriaan's computations suggest that about one percent of the available plastic can be broken down by these bacteria annually. However, she emphasizes that this value is likely an underestimate, as the study only measured carbon-13 in CO2, excluding other plastic breakdown products.
Promising Yet Incomplete Solution
Despite Rhodococcus ruber's breakthrough, this bacterial digestion of plastic is not the final solution to the pervasive plastic pollution in our oceans. The experiments are principally a proof of concept and answer the enigma of the 'missing plastic' in the oceans, providing a piece to the jigsaw of plastic degradation in aquatic environments.
While the preliminary findings suggest that real seawater and sediment bacteria might also degrade plastic, more research needs to be conducted to confirm these results and determine how much oceanic plastic bacteria can genuinely degrade.
Future Directions and Challenges
The power of plastic-eating bacteria, despite their promise, should not be viewed as the panacea to our plastic waste crisis. The sheer volume of plastic waste is colossal, and current plastic-eating bacteria work at a relatively slow pace.
Additionally, the potential environmental repercussions of introducing genetically engineered bacteria into natural environments are not entirely understood, fueling concerns about possible unintended consequences.
Thus, while research into plastic-eating bacteria should be pursued and could indeed form part of the solution, it must be complemented by substantial efforts to reduce plastic production and consumption, enhance recycling technologies and infrastructure, and develop eco-friendly alternatives to conventional plastics.
Overall, the work surrounding plastic-eating bacteria, such as Rhodococcus ruber, showcases nature's extraordinary adaptability and resilience. In concert with advancements in bioengineering, these microbes might significantly contribute to mitigating our most urgent environmental challenges. But, their use should form part of a broader, multifaceted strategy that includes reducing plastic use, improving recycling, and developing sustainable alternatives.
