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A cellular entity retaining only its replicative core: Hidden archaeal lineage with an ultra-reduced genome (www.biorxiv.org)

submitted 4 days ago by [email protected] to c/[email protected]

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Defining the minimal genetic requirements for cellular life remains a fundamental question in biology...Here, we report the discovery of Candidatus Sukunaarchaeum mirabile, a novel archaeon with an unprecedentedly small genome of only 238 kbp —less than half the size of the smallest previously known archaeal genome...lacking virtually all recognizable metabolic pathways, and primarily encoding the machinery for its replicative core: DNA replication, transcription, and translation. This suggests an unprecedented level of metabolic dependence on a host, a condition that challenges the functional distinctions between minimal cellular life and viruses...

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[–] [email protected] 3 points 4 days ago

As a junior biologist, I remember having the realization that viruses and other quasi-living things are just an epi-phenomenon of life. That was a level-up moment in my training, a lot of things clicked into place.

Meaning, if one could magically remove all viruses from the biosphere, they would re-evolve very quickly. Let alone the fact there are significant numbers of viral fragments in our DNA, some of which have been co-opted and used for crucial purposes, such as the mammalian placenta.

Plus the tendency of some of those fragments to move around the genome, providing a source of variation that is sometimes selected for.

Viruses and maybe this archaea may not meet a binary definition of ‘life’, but any biosphere anywhere in the universe will have things like them in great abundance. Any evolving system will produce them.