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Comment by grandinj | Hacker News Reader

These microbes are surprisingly hard to scale up i.e. to make them work on large amounts of product at a time. (My wife did research on such bugs for a while).

All sorts of things start happening once you have a lot of them, and the process becomes incredibly tricky to keep going.

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Do they get fat and lazy? [Maybe we should invent Netflix for microbes, then]

(Paraphrasing because of my limited understanding of what my wife did)

The biological pathway that makes them eat plastic is pretty card to keep activated. It's not a very profitable pathway, so the bugs tend to try eating other stuff if there is even a little available, or they are even a little outside the optimal range for eating plastic.

Interesting stuff, would love to hear more intuition about why this is difficult. Is it just that we haven't found an economical pathway for metabolizing plastics, or is there a fundamental reason why one should not exist?

Hydrocarbons have an energy density 2-3x higher than glucose, so naively it seems like there should be a profitable metabolic pathway!

Hydrocarbons are extremely stable, which means it requires a large energy input to break them up.

The article doesn't go into a lot of detail, but my guess is that the bacteria can break up the carbamate links.

As a basic analogy, think of it like human metabolism burning fat vs. carbohydrates. Fat is much more energy dense, but until you starve the body of carbohydrates, your body won't burn it. This pathway likely exists as a "backup" metabolic system so that in the absence of easy-to-digest feedstocks, the microbe can still live, but at an energetic cost.

Wonder if CRISPR or similar could be used to knock out regular metabolism pathways. Seems like they'd be understood enough to do so effectively.

Once those microbes become efficient, say goodbye to specific plastics as a durable material for regular use. The microbes wouldn't know the difference between trash and in-use material.

Unless the metabolic pathway requires some super-specific and limited resource, thus garbage facilities could supply the catalyst and the microbes would begin consuming the plastics.

Essentially none would survive outside designated plastic eating situations.

Until ... life finds a way ...

Given that this pathway is inefficient and plastics aren’t an inefficient food mechanism it seems likely even without a specific limiter it’d be hard for the bacteria to spread widely. Similar to the bacteria that termites host which decompose cellulose. But then again maybe plastic eating termites would co-evolve with such a bacteria. That’s creepy to think about. “My tv got eaten by plastic termites”... As you say life often finds a way.

> Until ... life finds a way ...

In particular, a mutation that drops the need for catalyst turns out to be metabolically beneficial.

Pretty sure they alude to that in Ringworld

Plastics are very chemically difficult to degrade. The nearest biological polymer is probably lignin, and even though it's part of a very porous matrix, it still takes years to break down.

I'm not too worried about PE, PET, PU, or nylon "rotting"

In a sense. They're highly specialized organisms with relatively inefficient metabolisms. They do great in an environment filled with just them and their food. But in an environment filled with other organic material (like their own bodies) they get outcompeted pretty badly by more conventional microbes.

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