Fungus-like organisms in deep time and deep rock | Hacker News Reader

Fungus-like organisms in deep time and deep rock

natureecoevocommunity.nature.com

84 pointsjelliclesfarm10 comments

The "fungus like" organism in a mutualistic relationship with bacteria is evocative of the structure and life style of the pre- or proto-eukaryotic Lokiarchaeota recently cultured and imaged by Hiroyuki Imachi et al.

"Isolation of an archaeon at the prokaryote–eukaryote interface". Nature. 577 (7791): 519–525. Bibcode:2020Natur.577..519I. bioRxiv 10.1101/726976. doi:10.1038/s41586-019-1916-6. PMC 7015854. PMID 31942073.

If fungi ancestors are 2.4 billion years old or older, that means there had to have been some sort of organic matter at least that far back as well. And if that’s the case, biology should be pretty widespread throughout the universe.

There was plenty of organic matter then, as that was around the time of the Great Oxygenation Event, when cyanobacteria were turning the Earth's atmosphere from reducing to oxidizing.

It still feels a bit weird that we call it an "event" when it took millions of years, and then another 800 million years before anything came along that could breathe oxygen, leading to bacteria repeatedly nearly killing themselves off during that entire period[0].

I wonder if this fungus-like discovery changes any of that story.

[0] https://www.patheos.com/blogs/daylightatheism/2009/02/bands-...

As a geologist, we can definitely have an unusual idea of what counts as "fast" :)

That's a good question, I would say if anyone found fungi before the GOE that would be a big surprise. Finding them after the GOE makes sense, so doesn't necessarily change our understanding of the GOE -- but if they really were around this soon after (if this article is correct) that would definitely seem to have interesting implications for the evolutionary origin of fungi.

Could it affect our understanding of the formation of these iron bands? I guess the funghi don't consume oxygen, or it wouldn't have taken those 800 million years, but if they're that old shouldn't we find them in the bacterial mats, decomposing stuffe affecting the chemistry?

Hmm, good question. There is generally expected to be plenty of decomposition (or in biogeochemical speak "remineralization") happening any time you have enough organic carbon around (and enough of a chemical potential gradient between that and some oxidant) for somebody to make a living respiring that organic carbon. And just in terms of biogeochemical cycling the result is pretty similar whether the decomposition is being done by heterotrophic bacteria and archaea, or by fungi -- so to first order it wouldn't change that. Nonetheless, there might be some unexpected consequences if a significant proportion of the remineralization was being done by fungi.

There's an interesting idea that the evolution of large genomes in eukaryotes was driven by the need to deal with oxygen.

https://www.quantamagazine.org/dnas-histone-spools-hint-at-h...

For reference, I assume the renewed interest here is driven by the recent speculation about fungus-like organisms on Mars https://twitter.com/i/web/status/1390423317245530124

And as a twitter reply pointed out aptly, the first author is a well-known quack. See also https://www.cnet.com/news/sorry-nasa-photos-are-not-evidence....

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