Re: Irreducible like form?

On 7/1/2025 10:51 AM, erik simpson wrote:

https://www.biorxiv.org/content/biorxiv/ early/2025/05/02/2025.05.02.651781.full.pdf
 A cellular entity retaining only its replicative core: Hidden archaeal lineage with an ultra-reduced genome
 Abstract
 Defining the minimal genetic requirements for cellular life remains a fundamental question in biology. Genomic exploration continually reveals novel microbial lineages, often exhibiting extreme genome reduction, particularly within symbiotic relationships. 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— from a dinoflagellate- associated microbial community. Phylogenetic analyses place Sukunaarchaeum as a deeply branching lineage within the tree of Archaea, representing a novel major branch distinct from established phyla. Environmental sequence data indicate that sequences closely related to Sukunaarchaeum form a diverse and previously overlooked clade in microbial surveys. Its genome is profoundly stripped-down, 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. The discovery of Sukunaarchaeum pushes the conventional boundaries of cellular life and highlights the vast unexplored biological novelty within microbial interactions, suggesting that further exploration of symbiotic systems may reveal even more extraordinary life forms, reshaping our understanding of cellular evolution.
 

The description in the paper indicates that it is evolving to be a virus like parasitic bacterium.  It doesn't contribute to host metabolism like mitochondria or photosynthetic symbionts and just seems to suck resources out of the host in order to replicate itself.  It controls it's own replication, but relies on the host for resources to replicate itself.  It seems to be turning into a virus-like bacteria.  It isn't an example of a minimal genome (it relies on the host for it's metabolic needs).  It seems to be a genome that is required to maintain it's parasitic lifestyle.
Ron Okimoto