The Cellular Secret to Resisting the Pressure of the Deep Sea | Hacker News Reader

The Cellular Secret to Resisting the Pressure of the Deep Sea

quantamagazine.org

88 pointsBrajeshwar12 comments

Interesting small creatures, which (as a side note) can have enormous ecological impacts as the Wikipedia article mentions:

"On the other hand, in the late 1980s the Western Atlantic ctenophore Mnemiopsis leidyi was accidentally introduced into the Black Sea and Sea of Azov via the ballast tanks of ships, and has been blamed for causing sharp drops in fish catches by eating both fish larvae and small crustaceans that would otherwise feed the adult fish."

https://en.wikipedia.org/wiki/Ctenophora

What would be a solution to carrying lifeforms elsewhere in the ballast tanks? Turning the water over regularily to reduce the distances that these creatures can travel aboard?

> Archaea lipids behave differently than those found in bacteria and eukaryotes

That's a hell of a thing to drop with no further explanation. I thought eukaryotes were supposed to have evolved from basically archaea, or at least very archaea-like ancestors. How do eukaryotes end up sharing chemistry with bacteria but not archaea?

The eukaryotes share most of their metabolic paths with bacteria instead of archaea, not only their membrane composition.

Because all the known eukaryotes have their origin after the symbiosis with the bacteria that have become mitochondria and most of the genome of the mitochondria has been moved to the nucleus, one possibility is that all the bacterial characteristics of the eukaryotes come from the ancestor of mitochondria.

There are alternative hypotheses, e.g. that there have been a few other symbiosis events with some bacteria, before the symbiosis with the ancestor of mitochondria, so some of the bacterial characteristics are inherited from different bacteria.

A possibility is that some of the differences between archaea and bacteria have arisen after the divergence between archaea and eukaryotes, so the bacterial characteristics of the eukaryotes would be primitive. However this supposition has become more unlikely during recent years, because some evidence has accumulated that appears to support a closer relationship between eukaryotes and some of the archaea than with the other archaea, in which case all characteristics shared by all archaea would predate the divergence with the eukaryotes.

It's one of the problems with the 'current' model of Eukaryogenesis. Eugene Koonin has recently suggested an interesting two stage model based also on shared virus phylogenies: https://www.nature.com/articles/s41564-023-01378-y

Bacterial genes migrating from the mitochondria to the nucleus -- or at least, that's the theory I read in "The Vital Question" by Nick Lane.

Archae have ether linkages in their lipids, bacteria and eukaryotes have glycerol esters.

I don't really understand what's the “problem” with high pressure for living things: they are full of water at the same pressure as the surrounding water so there's no risk to be crushed, so it's not clear to me what “resisting the high pressure” means.

It seems to be more about the different chemical properties of proteins under pressure, rather than structural problems that come with pressure difference. Just like e.g. water has a higher boiling point when pressurized, all kinds of chemical processes are different under pressure.

They talk about it in the article. The last figure shows what happens to the normal membrane at high pressures, it becomes too stiff/compressed and therefore cannot function (i.e. let things through etc)

Very interesting - it is as if the healthy membrane shape is the target bytecode to which the varying "source" shapes in varying categories of jellies converge to under varying temperature/pressure conditions in order to live.

So is the idea that the behavior of the deep sea membrane, which is like a compressed spring, could be mimicked in artificial materials to resist high pressures?

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