I always wonder how long it’s gonna take before plastic-eating bacteria start to proliferate in the wild. There was a while back in prehistory when there was no microbe in existence that could eat wood and trees were almost immortal, and that’s how we got certain fossil fuels, because when a tree died by getting knocked over by wind or whatever, the wood went into the ground undigested. I think. The main appeal of plastic is that it’s currently nigh on invincible to microbial attack and so is perfect for sealed containers (when you need to keep something fresh and preserved), but I assume eventually plastic will be just as prone to rot as cardboard. I wonder, will glass then make a comeback?
Those molecules contain lots of chemically accessible bonds, especially C–O bonds. Plants built them using biological chemistry, so other biological chemistry can, in principle, take them apart.
An enzyme isn’t a tiny animal chewing through plastic. It has to contact a polymer chain, bind it in an active site, chemically cleave a bond, release the products, and repeat.
A plastic can thwart that by being:
hydrophobic + highly crystalline + insoluble + chemically repetitive + physically inaccessible.
There’s no evolutionary law saying organisms must eventually become capable of rapidly consuming any energetically favorable substance.
Evolution has to find a chemically feasible pathway. And even if it does, decomposition might be:
plastic bottle → 150 years
rather than
plastic bottle → three weeks.
And amusingly, we could simply change the plastic. If PET suddenly became unsuitable for decades-long applications because PET-eating microbes became ubiquitous, we’d manufacture polymers resistant to those enzymes, add protective layers, alter crystallinity, or use different polymers.
All and all, I’m doubtful microbes will come to our rescue. Unless we engineer them for the task, that is.
The catch is that “can eat plastic” and “can solve plastic waste” are very different thresholds.
The bacterium almost completely degraded a PET film in about six weeks at 30C. But that film was extremely favorable material, thin and only about 1.9% crystalline.
That’s important because a real PET bottle is much harder. PET chains in crystalline regions are packed tightly together, and the enzyme has trouble getting the polymer into its active site. Typical waste PET can have crystallinity above ~25%.
PET happens to contain chemically convenient ester bonds:
PET chain → ester bond → PETase can hydrolyze it
Whereas polyethylene is basically:
–C–C–C–C–C–C–
There’s no corresponding easy hydrolysis reaction. That’s a much harder biochemical problem.
So if you dumped P. sakaiensis into a landfill, it wouldn’t start consuming “the plastic.” It would encounter a giant mixed pile, only some of which is PET, and much of that PET would be physically difficult for it to attack.
Maybe we can engineer something inspired by P. sakaiensis. I don’t think it overcomes the bigger hurdles by itself, though.
No, but there is a great prize for any organism that figures it out and unlocks all that plentiful energy, especially if it encodes the “recipe” for future generations.
And that’s just natural selection. Artificial selection could possibly speed that up, too, if it’s actually possible.
Artificial selection has got to be possible, given we’ve done it to our fruit merely by happenstance over the generations. And our dogs, too.
I wonder if plastic would be more like diamond. We don’t see enzymes breaking down diamond, even though that’s been around for plenty of time.
Natural selection could probably get there if the conditions are right, just as artificial selection could probably force those conditions in a lab. Yet I feel the it’s probably much less likely than was the case with wood.
Artificial selection has got to be possible, given we’ve done it to our fruit merely by happenstance over the generations. And our dogs, too.
No, I wasn’t clear. I meant for the “it” in my sentence to refer to biologically breaking down plastics, not to refer to artificial selection.
If, for example, wax moth caterpillars can break down polyethylene in small quantities in certain concentrations, then perhaps artificial selection can amplify that effect by expanding the range of concentrations that can be treated that way, or otherwise improving efficiency or volume of processing, etc.
Actually, you make a really valid point, but it’s leading me to an unfortunate conclusion.
If bacteria was developed that could break down plastics and did actually break free to start digesting plastic in the wild, that would really clean up the earth, for maybe 10 years. But then the manufacturers would start using “more durable” materials, they’d slightly change their plastic chemistry to resist these microbes and we’ll be in the same boat we’re in now, where plastics don’t break down.
Because the thing is, one of our primary uses for plastic is when we want a material that won’t rot or rust, so breaking down defeats is purpose. We want plastic to not break down, so our products continue to work longer. But we also want plastic to break down, to not pollute our environment. These two goals are completely at odds with each other. The result is, and I now 100% believe this, we will never really have bacteria that breaks down plastic, long lasting plastic waste is a product of our own desire for “quality” products.
Yeah we need whatever microbes break down plastic to remain isolated so that we can break down plastic when we want to but it remains “invincible” otherwise.
I always wonder how long it’s gonna take before plastic-eating bacteria start to proliferate in the wild. There was a while back in prehistory when there was no microbe in existence that could eat wood and trees were almost immortal, and that’s how we got certain fossil fuels, because when a tree died by getting knocked over by wind or whatever, the wood went into the ground undigested. I think. The main appeal of plastic is that it’s currently nigh on invincible to microbial attack and so is perfect for sealed containers (when you need to keep something fresh and preserved), but I assume eventually plastic will be just as prone to rot as cardboard. I wonder, will glass then make a comeback?
Wood is a biological material made from molecules that have been sitting in Earth’s biosphere for hundreds of millions of years:
Wood
→ cellulose
→ hemicellulose
→ lignin
→ sugars/aromatic compounds
→ microbial metabolism
Those molecules contain lots of chemically accessible bonds, especially C–O bonds. Plants built them using biological chemistry, so other biological chemistry can, in principle, take them apart.
An enzyme isn’t a tiny animal chewing through plastic. It has to contact a polymer chain, bind it in an active site, chemically cleave a bond, release the products, and repeat.
A plastic can thwart that by being:
hydrophobic + highly crystalline + insoluble + chemically repetitive + physically inaccessible.
There’s no evolutionary law saying organisms must eventually become capable of rapidly consuming any energetically favorable substance.
Evolution has to find a chemically feasible pathway. And even if it does, decomposition might be:
rather than
And amusingly, we could simply change the plastic. If PET suddenly became unsuitable for decades-long applications because PET-eating microbes became ubiquitous, we’d manufacture polymers resistant to those enzymes, add protective layers, alter crystallinity, or use different polymers.
All and all, I’m doubtful microbes will come to our rescue. Unless we engineer them for the task, that is.
Those bacteria already exist.
https://en.wikipedia.org/wiki/Pseudideonella_sakaiensis
The catch is that “can eat plastic” and “can solve plastic waste” are very different thresholds.
The bacterium almost completely degraded a PET film in about six weeks at 30C. But that film was extremely favorable material, thin and only about 1.9% crystalline.
https://pmc.ncbi.nlm.nih.gov/articles/10546322/
That’s important because a real PET bottle is much harder. PET chains in crystalline regions are packed tightly together, and the enzyme has trouble getting the polymer into its active site. Typical waste PET can have crystallinity above ~25%.
https://doi.org/10.1007/s42452-025-07764-x
Also, P. sakaiensis attacks PET, which is a polyester. It does not give us a general solution for:
PET happens to contain chemically convenient ester bonds:
Whereas polyethylene is basically:
There’s no corresponding easy hydrolysis reaction. That’s a much harder biochemical problem.
So if you dumped P. sakaiensis into a landfill, it wouldn’t start consuming “the plastic.” It would encounter a giant mixed pile, only some of which is PET, and much of that PET would be physically difficult for it to attack.
Maybe we can engineer something inspired by P. sakaiensis. I don’t think it overcomes the bigger hurdles by itself, though.
There’s a yeast for it now too:
https://www.ucc.ie/en/sefs/news/news2026/researchers-at-ucc-engineer-yeast-to-recycle-plastic-more-sustainably.html
No, but there is a great prize for any organism that figures it out and unlocks all that plentiful energy, especially if it encodes the “recipe” for future generations.
And that’s just natural selection. Artificial selection could possibly speed that up, too, if it’s actually possible.
Artificial selection has got to be possible, given we’ve done it to our fruit merely by happenstance over the generations. And our dogs, too.
I wonder if plastic would be more like diamond. We don’t see enzymes breaking down diamond, even though that’s been around for plenty of time.
Natural selection could probably get there if the conditions are right, just as artificial selection could probably force those conditions in a lab. Yet I feel the it’s probably much less likely than was the case with wood.
No, I wasn’t clear. I meant for the “it” in my sentence to refer to biologically breaking down plastics, not to refer to artificial selection.
If, for example, wax moth caterpillars can break down polyethylene in small quantities in certain concentrations, then perhaps artificial selection can amplify that effect by expanding the range of concentrations that can be treated that way, or otherwise improving efficiency or volume of processing, etc.
Actually, you make a really valid point, but it’s leading me to an unfortunate conclusion.
If bacteria was developed that could break down plastics and did actually break free to start digesting plastic in the wild, that would really clean up the earth, for maybe 10 years. But then the manufacturers would start using “more durable” materials, they’d slightly change their plastic chemistry to resist these microbes and we’ll be in the same boat we’re in now, where plastics don’t break down.
Because the thing is, one of our primary uses for plastic is when we want a material that won’t rot or rust, so breaking down defeats is purpose. We want plastic to not break down, so our products continue to work longer. But we also want plastic to break down, to not pollute our environment. These two goals are completely at odds with each other. The result is, and I now 100% believe this, we will never really have bacteria that breaks down plastic, long lasting plastic waste is a product of our own desire for “quality” products.
Yeah we need whatever microbes break down plastic to remain isolated so that we can break down plastic when we want to but it remains “invincible” otherwise.
That would be really cool if so. Except for Blahaj. Don’t eat Blahaj. >:(