(Order of authorship in the original publication: Imachi, Nobu, Nakahara...Takai.) The authors report that after 12 years of research they have cultured a microorganism that may be the transitional species between prokaryotes and eukaryotes. The organism, obtained from deep ocean sediments, they named Prometheoarchaeum syntrophicum. It has a large number of genes that encode eukaryotic signature proteins only found in eurkaryotes. This bacterium has long tentacle-like protrusions emanating from its surface, and its metabolism characteristics prompted the authors to propose a new model for the emergence of the first eukaryotic cell. Instead of the classic phagocytosis concept of one cell eating another, the authors proposed that this host archaeon connected to the metabolic partner using the newly discovered tentacular extracellular structures and simultaneously formed a primitive chromosome surrounding structure that is topologically similar to the nuclear membrane.

"On the basis of the available data obtained from cultivation and genomics, and reasoned interpretations of the existing literature, we propose a hypothetical model for eukaryogenesis, termed the entangle–engulf–endogenize (also known as E³) model." (From the abstract.)

(Thanks to Juan Weiss for this reference and its interpretation.)

Open source from Nature.com at this link.