[MaeveChondrally (OP)]

Is there an enzyme that decomposes plastic that is secreted by a naturally occuring microbe?
Can we put its DNA in algae and get rid of the plastic in the ocean?
Is this type of genetic engineering safe?
Is it really our only option for getting rid of this plastic in a reasonable period of time?
Would the microbe be safe to unleash on the environment?

[Eternal Student]

Hi.

Is there an enzyme that decomposes plastic that is secreted by a naturally occuring microbe?

    The old answer would have been a clear "No, there isn't".   It's also the reason why plastic is used the way it is used.    You can have plastic window frames and plastic garden furniture because it isn't espected to rot away, no microbes attack it.
    More recently there have been some indications that micro-organisms are evolving to have enzymes that can attack plastic.  At the moment these enzymes attack only a small set of plastics.
    Here's one article that provides some more info:
https://www.theguardian.com/environment/2021/dec/14/bugs-across-globe-are-evolving-to-eat-plastic-study-finds

Best wishes.

[alancalverd]

Way back in the Sixities, BBC TV ran a series called "Doomwatch" - nearly believable sci-fi mixed with a semi-secret government investigatory department, and probably the reason I joined the scientific civil service. One of the episodes revolved around a plastic-eating bug that first infected an airplane then spread to all sorts of Dali-esque scenes of melting, oozing, and short circuits: a good idea that got out of hand.

Often the problem with biological systems: if they have no predators, they eat everything, including the stuff we need.  Natural and artificial enzymes are fine. The natural ones exist in species that are held in check by their predators, and the artificial ones can be neutralised, but if you engineer a living and reproducing bug with no predators, you can end up with a plague.

[Eternal Student]

Hi again.

One of the episodes revolved around a plastic-eating bug that first infected an airplane then spread to all sorts of Dali-esque scenes

    The standard procedure for an engineered microbe that expresses a desired enzyme is to deliberately weaken that microbe.  Knock out some DNA that is required for it to manufacture something essential.   Then you can retain control over the microbe by just feeding it - putting that essential component into its environment so that the microbe can absorb it.  When the feeding stops the microbe should die out.   Now microbes reproduce very rapidly and evolution can take place over just a few years so there's a risk of mutation to create a subspecies that can survive without the articifical supply of that nutrient.  However, you can reduce that risk by weakening the microbe in two or more areas and not just one.
      I'm no expert in microbiology but I think the biggest problem is that you can't hope to control all the other microbes that already exist out in the world.   If you've introduced the DNA for a plastic enzyme into a plasmid of your engineered microbe then there is a risk that this plasmid may be accidentally incorporated into some other species of bacetria:  The engineered bacteria will keep dying and spilling their contents out in the vicinity of other bacteria, over time it's almost inevitable that some of those plasmids will get inside another bacteria.
     Another significant risk is just that a symbiotic system can be created.  There are a lot of other bacteria out there and they might very well be able to use some of the broken down plastic products where the engineered bacteria are deploying their enzyme.  Now those ordinary other bacteria will die quite often and spill their contents including the nutrients that the engineered bacteria couldn't make into the area around the engineered bacetria.   So you have the potential for a very simple symbiotic system without the need for anything more complicated than that to evolve.
     Anyway, that's what I would have thought.  It's not the engineered bacteria that is the biggest concern, it's all the other bacteria in the world that you can't control.

Best Wishes.
 

[alancalverd]

....or the ones you take home from the lab in your hair and clothes - or nibbling at your pen.

No need to wait for mutants: one infected bat seems to be enough to disrupt society around the world. How many engineered plastiphages would it take to set technology back a hundred years?   

[evan_au]

A researcher who also kept bees found some parasitic waxworms in her beehive.
She removed these parasites from the hive, and put them in a plastic bag - but they managed to corrode holes in the polyethylene bag (which is chemically very stable).
It turns out that the microbes that help the waxworms digest beeswax can also break down polyethylene...
https://www.usatoday.com/story/news/nation/2020/03/06/waxworms-caterpillars-eat-plastic-pollution-but-could-also-hurt-bees/4952495002/

[Eternal Student]

Hi again and thanks for the input alancalverd and evan-au.

So bringing it all back together and addressing @MaeveChondrally  ' s questions:

Is there an enzyme that decomposes plastic that is secreted by a naturally occuring microbe?

   Partially.   There are some enzymes that have some effect on some plastics.  It may not be all that effective at the moment.   A general solution to the problem of degrading plastics might involve producing multiple enzymes to attack a wider variety of plastics.   See earlier discussions.

Can we put its DNA in algae and get rid of the plastic in the ocean?

    Some algae have plasmids similar to bacteria.   This would presumably be the easiest way to bio-engineer the algae to produce a certain enzyme.   I'm not sure of the rate of production of proteins from DNA in such plasmids but I believe it is generally a much lower rate than you'd expect from bacteria.   This could make algae much less efficient at breaking down plastics.   
     If you were trying to get the DNA into the nucleus where the transciption rates would generally be much higher than this is a more difficult task to achieve.   There is CRISPR biotechnology that stands a chance of getting the DNA sequence into the nucleus but placing it somewhere in the DNA that is routinely read could be much more of a difficult task.  It might involve a lot of trial and error until you get the DNA sequence inserted somewhere so that it is routinely transcripted but you haven't seriously disrupted the normal functions of the cell.  (I don't know, as I stated I'm not an expert in microbiology or algae).
    Over-all then,  the answer I'd stick with is  "probably yes we can get the DNA into some algae but there may be very limited production rates of the enzyme".

Is this type of genetic engineering safe?

    I'm not the commitee that decide what applications of genetic enegineering are safe or acceptable, or indeed if we should be experimenting with genetic engineering at all.   There doesn't seem to be world-wide agreement on genetic engineering.
   See:  https://en.wikipedia.org/wiki/Regulation_of_genetic_engineering

    As outlined in the earlier discussions, this particular application - producing an organism that can attack and degrade plastics, could carry significant risks.   It could undermine all the existing uses and applications of plastic.   My own opinion on the matter is of little consequence but I would have thought that releasing such a genetically engineered algae or bacteria into the world is an unacceptable risk.   Using the engineered organisms in a controlled space, for example in a sealed area at a waste processing centre where plastics can be brought in to be broken down, would be the better option.   (Realistically, eventually the organism will get out by some accident or other but it should be weakened sufficiently so that it won't survive, as previously discussed.   Reducing the amount of time that the organism is in the outside world should make it extremely unlikely for any of the issues like spontaneous mutations in the organism etc. to happen).

Is it really our only option for getting rid of this plastic in a reasonable period of time?

     I don't know.   It sounds like the lazy alternative to just stopping the widespread use of plastics and the unsatisfactory ways of disposing of it (like burrying it in a land-fill site).

Would the microbe be safe to unleash on the environment?

    This has been the focus of much of the discussion.   Probably not,  although you can mitigate some of the risks if the world has time to prepare for the eventuality that plastics will soon be degradeable materials.   You need to get the plastics out of critical engineering applications like the computer systems that control nuclear power stations,  the hulls of boats used by the lifeguards,  the insulation that prevents the wires in your house electrical system from short circuiting etc.   An alternative might be to set up regular integrity checks of these materials similar to the sort of thing that should be done when already degradeable materials like wood have been used in engineering applications.

Best Wishes.

[Colin2B]

A researcher who also kept bees found some parasitic waxworms in her beehive.

These waxworms (also known as mealworms) are very common in beehives, in the wild they serve a useful purpose in clearing old wax out of tree trunks, chimneys etc abandoned by bees.
Over winter we put unused comb in plastic bags to keep the moths out, but if any eggs are inside the moth larvae will eat their way out of the bags. They also eat through wood and polystyrene, but some hard plastics seem to defeat them