Parakaryon

Parakaryon is a genus of single-celled organisms known from the species Parakaryon myojinensis. Its described cells combine features associated with prokaryotes and eukaryotes.

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Parakaryon myojinensis: A single-celled organism described from a specimen collected near Japan’s Myōjin Knoll, with a mixture of prokaryotic and eukaryotic features. This is the only described species assigned to the genus.
Myōjin Knoll: A submarine volcanic formation in the Izu-Bonin arc south of Japan. The specimen used to describe Parakaryon myojinensis was collected near this seamount.
Peptidoglycan: A mesh-like polymer of sugars and amino acids that forms the bacterial cell wall. A peptidoglycan-like wall was reported as one of the cell’s bacterial-associated features.
Phylogenetics: The study of evolutionary relationships among organisms using inherited characteristics and molecular data. A reliable placement for Parakaryon requires evidence of its evolutionary relationships.
Prokaryote: An organism whose cells lack a membrane-bound nucleus and other membrane-bound organelles. Parakaryon cells have bacterial-like traits but also structures unlike typical prokaryotic cells.
Izu-Bonin arc: A volcanic island arc formed above a subduction zone south of Japan. Its deep-sea environment provides the geographic setting for the known Parakaryon specimen.
Ribosome: A molecular machine that translates messenger RNA into proteins. The reported cytoplasm contains ribosome-like particles arranged in an unusual pattern.
Ribosomal RNA: RNA molecules that form core structural and functional components of ribosomes. Ribosomal RNA comparisons could help classify Parakaryon if suitable sequence data become available.
Eukaryote: An organism whose cells contain a membrane-bound nucleus and other membrane-bound organelles. Parakaryon has a nucleus-like compartment despite its atypical cellular organization.
Eukaryogenesis: The evolutionary emergence of eukaryotic cells from earlier cellular lineages. Parakaryon’s mixed traits invite comparison with questions about how eukaryotic organization arose.