Bugs Evolve That Can Eat PET Plastics Used In Bottles And Textiles: One of the modern environmental scourges created by people, namely the non-biodegradable plastic PET bottle, can now be eaten by bacteria. We only created this synthetic molecule 70 years ago – we still can’t efficiently recycle it – but the bacterium Ideonella sakaiensis can! Don’t underestimate the power of microbes.
Those of us who have worked with microbes are well aware of their powerful potential to adapt to new environments. Nearly 40 years ago I carried out research on Enterococcus in the Bacteriology Department at Manchester University Medical school. My dissertation? Well these little organisms that live in the human gut were able to transmit little pieces of genetic information between one another during sex (or ‘conjugation’ as bacteria prefer to call it). This genetic information (small circular pieces of DNA called plasmids) contained the genes for multiple antibiotic resistance.
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When humans have sex they sometimes share sexually transmitted diseases with one another. When bacteria have sex they can pass on things that are much more useful – like immunity to the powerful antibiotics we use to try and kill them. These are the same antibiotics we feed in abundance to our cows, sheep, pigs and chickens – and guess where the plasmids with antibiotic resistance probably originated? Considering their intelligent application of sex it is hardly surprising that there are a lot more bacteria in the world than people (in fact 90% of the cells in our ‘own’ bodies are microbes!).
Due to my familiarity with bacterial ingenuity I was not surprised when on March 11th 2016 researchers in Japan announced that they had isolated a strain of bacteria that eats PET plastic. They named this PET eater Ideonella sakaiensis. It was discovered by Shosuke Yoshida and co-workers at the Kyoto Institute of Technology using samples taken from the soil and waste water around Japanese plastics recycling plants.
I remember from my own time living in Japan (30 years ago) that this nation was one of the first to seriously embrace plastics recycling so presumably the local bugs have had a bit longer to evolve the necessary enzymes. However, in evolutionary terms, this is an incredibly short period of time to develop new protein based enzyme systems. In this case the enzymes can break down a man made plastic that did not exist over 70 years ago.
The newly discovered bacteria has evolved two enzymes which systematically break down the synthetic polymer that PET is made up of. You can think of this polymer as a microscopic chain of tough beads which are connected by an almost unbreakable thread. Well the bacteria is able to break down this thread separating the polymer into the individual beads (known as monomers). It then breaks down these monomers into two smaller chemical components (ethylene glycol and terephthalic acid) which it can digest using in normal biological processes to derive food and energy.
This development opens up a couple of interesting possibilities. On the one hand the bug Ideonella sakaiensis could be used itself to break down PET based plastics. There is however one snag – at 30C it takes about 6 weeks to totally break down a piece of plastic the size of a finger nail. The second possibility involves genetic engineering techniques. The genes which contain the genetic information to produce the two new proteins could be isolated from this bacteria and then inserted into another faster growing bacteria like E.coli.
This idea of inserting a ‘foreign’ gene into a different bacteria is hardly new. It is not that dissimilar to the approach I used many years ago when transferring my plasmids for antibiotic resistance. However today it is possible to use special gene ‘cut and paste‘ enzymes to specifically place a new gene into a bacteria’s chromosome (typical enzymes used are called ‘restriction endonucleases‘). Rather than my primitive system requiring bacterial sex the modern approach uses different carrier (vector) systems to get the genes (DNA) into the microbes. For example they can use viruses (bacteriophages) that infect bacteria by injecting their DNA into them. Molecular geneticists add the foreign gene to the viruses own DNA so they are injected into the bacteria together.
The scientific community is quite excited by the prospects of harnessing microbial ingenuity to help us clear some of the rubbish that we ourselves have created through overuse of plastics. However I think one point has been overlooked by those trying to make use of this rapid evolutionary development. One of the reasons we started using plastics in place of materials like wood, cardboard and paper was their inertness. With plastic bottles and films people did not have to think about the shelf life of the packaging because usually the contents go off much quicker.
However in a world in which bugs can now break down our plastics products it may not be long before people start to discover their packaging is not as inert as they thought. Although Ideonella sakaiensis can take about 6 weeks to break down a small piece of plastic this is just the beginning. As a result of evolutionary ‘survival of the fittest‘ – more efficient plastic eating bacteria will quickly evolve. Soon those PET water bottles on the shelf could start leaking after just a few weeks. Through our thoughtless overuse of plastics (as with antibiotics) we have potentially destroyed the usefulness of what was an incredibly useful and hygienic packaging material. Watch this space!
The original paper about the discovery of this microbe “A bacterium that degrades and assimilates poly(ethylene terephthalate)” published in Science on March 11th 2016 by Shosuke Yoshida et al can be found using the link here.
Chris Duggleby started his scientific career studying Bacteriology and Virology at the Manchester University Medical School. From there he went on to spend over 35 in the chemicals and oil industries which included setting up a polymers research and development group in Geneva, Switzerland for a major international chemicals company. Following an MBA from Warwick University he went on to lead a number of international manufacturing and marketing operations in the Chemicals, Plastics and Oil industries. This included being the founding President of Formosa BP Chemicals Corporation in Asia. His work involved living and working in Europe, Asia, the USA, the Middle East, and Russia. More recently he was invited to take on a senior leadership position in the Audit Department of the BP International Oil Group. Here he used his global change and risk management experience to help the group reshape its management structures and processes following a major environmental disaster in the Gulf of Mexico. He has now retired to focus on writing about risk management and producing music in his studios near London, in the Alps and Cape Town. If you are interested in risk management check out his RiskTuition.com or BizChangers.com (management of change) sites. He has also recently launched the JointVentureRisk.com site.
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2 thoughts on “Bugs Evolve That Can Eat PET Plastics Used In Bottles And Textiles”
I actually understood some of this. You are a good explainer, I guess. This has the potenetial of being able to clear up the floating islands of garbage where ocean currents meet except that their are those who want to leave these islands along because they are habitat for various ocean organisms and fish. My sense of tidiness wants to clean them up anyway.
Thanks Linda, this is great feedback. These bugs are evolving very rapidly and they may force us to reconsider the way we use plastics. People are unlikely to want a bottle which starts rotting after a couple of weeks (or less). Perhaps glass will make a comeback!