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eniteris OP t1_it1f00x wrote

Reply to comment by JohnFByers in Novel multicellular prokaryote discovered next to an underground stream by eniteris

It's not just filamentous colonies or biofilms, but the differentiation into different life stages and the formation of what appears to be a fruiting body that's interesting. Also reacts to being submerged in water.

And it's a novel multicellular prokaryote, not novel multicellularity in general.

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JohnFByers t1_it1foiy wrote

This remains a unicellular prokaryote capable of colonial formations. It may provide indications about a potential evolutionary path toward multicellularity, but I don’t see any data that it has achieved multicellularity.

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eniteris OP t1_it1g168 wrote

Multicellularity is a spectrum with no hard cutoff, unless you would like to personally provide one?

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JohnFByers t1_it1kqlg wrote

Temporal and spatial regulation of gene expression that generates cell lineages comprising interdependent cells with a common genome. Among the metazoans, Porifera have a totipotent and rudimentary stem cell system that still provides mechanisms of development and differentiation. Transdifferentiation remains differentiation and I just see it as the basis of cellular plasticity.

Having dabbled in PDZ domains (before they were named PDZ domains and we just called them discs-large-like domains), I was pleasantly surprised to see recently the discovery of essentially intact post-synaptic density components in a multicellular eukaryote lacking a nervous system — the signalling and scaffolding components were there nonetheless.

Granted, other mechanisms of cell signalling exist that do not rely on animal-style junctions. But the other criteria remain challenging. If we do impose a common genome limitation, which I am convinced is appropriate, then prokaryotes with their relatively widespread propensity toward lateral gene transfer will be even more challenging to accept as anything beyond colonial.

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