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JohnFByers t1_it022io wrote

Filamentous colonies and biofilms are not novel.

This is not a multicellular species.

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eniteris OP t1_it1f00x wrote

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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