I thought this was interesting: https://www.cell.com/cell/fulltext/S0092-8674(26)01016-0

An amoeba has been found that functions at temperatures up to 63C. Hitherto only thermophile bacteria and archaea have been found that can tolerate such temperatures. It seems the amoeba relies on some biochemical features similar to these bacteria and archaea, the most striking of which is proteins with a net +ve charge. Apparently the repulsion between strands that this creates can inhibit the clumping and denaturing that might otherwise occur at high temperatures. They say it looks as if this similarity is due to convergent evolution. So presumably it has not arisen by some kind of horizontal gene transfer.

What I found myself wondering is how this compares with tardigrades. These are multicellular eukaryotic animals that seem remarkably resistant to extreme conditions. Has anyone done work on how these creatures manage it?

The authors acknowledge it, but I want to emphasize that neat things about this paper is not the fact that there are thermophilic eukaryotes. But rather the 3-4 degrees in excess of 60 C. The reason is that key studies in the 70s looked at heat tolerant fungi and based on this and similar studies, it was reasoned that around 60C is likely the upper thermal limit for eukaryotes. This study pushes it a few degrees higher and it will come down to really fine nuances.

Cool!

On 9/27/2026 at 8:23 AM, CharonY said:

around 60C is likely the upper thermal limit for eukaryotes

Why are eukaryotes so limited compared to prokaryotes?

There are multiple hypotheses. One is that eukaryotes have intracellular compartments and organelles, which have to be able to selective macromolecules (plus there is a lot of veiscle trafficking to sustain that). It is assumed that this relatively active and leaky membrane system cannot be built in a heat-resistant way. Thermophiles have modified membranes with lower fluidity, for example.

On 9/28/2026 at 1:41 AM, CharonY said:

There are multiple hypotheses. One is that eukaryotes have intracellular compartments and organelles, which have to be able to selective macromolecules (plus there is a lot of veiscle trafficking to sustain that). It is assumed that this relatively active and leaky membrane system cannot be built in a heat-resistant way. Thermophiles have modified membranes with lower fluidity, for example.

I’m interested in this business about +ve charged proteins. That seems, from the paper, to be the first time this has been seen in eukaryotes. Is that right?