Prokaryote or eukaryote? A unique microorganism from the deep sea (2012)

A recent discussion on HN [1] got me to reading Nick Lane's fascinating book, "The Vital Question." The book discusses (among other points) the origin of eukaryotes, and the mystery of why they have come to be only once in the history of life on earth.

The epilogue to the book was about the discovery of a single-celled organism in hydrothermal vents in the Pacific that could have been a true "missing link" - the formation of a new eukaryotic cell in progress. Unfortunately only once specimen was recovered - and then used up during prep for electron-microscopy - so its genome could not be sequenced.

[1] https://news.ycombinator.com/item?id=31789045 Wiki: https://en.wikipedia.org/wiki/Parakaryon_myojinensis