Scientists grow our closest microbial relatives in the lab for the first time

Scientists in Japan have grown, for the first time, two strains of the microbes thought to be the closest known relatives of the cells that make up humans, animals, plants and fungi. Led by Hiroyuki Imachi and Masaru K. Nobu of JAMSTEC, with Satoshi Nakagawa of Kyoto University, the team cultivated two strains of Heimdallarchaeia, named HC1 and SC1. The work was published in Nature on 28 October 2026.

Until now, these archaea had only been studied through DNA recovered from the environment, so their cell structure and way of life had never been checked in living cells. The microbes were grown from samples taken from a gas well in Chiba, Japan.

The findings went against some predictions. Inside, both strains were simple: no nucleus and no other membrane-bound compartments, the structures that define complex cells. Outside, they were complex, with long, branching membrane protrusions that gripped partner microbes, including methane-producing archaea they depend on to grow. They feed on peptides and live by depending on partners.

Both strains live without oxygen and are sensitive to it. But one carried several systems that protect it from oxygen, and it grew even when small amounts of oxygen were present at the start, as long as oxygen-using bacteria were alongside it.

Why it matters

How complex cells first appeared is one of biology’s biggest unanswered questions. The leading idea is that the first complex cell formed when an archaeon teamed up with a bacterium that later became the mitochondrion, the cell’s energy-producing part.

The results suggest the archaeon’s outside may have become complex first. Its long surface arms could have helped it build close partnerships long before a nucleus evolved. And oxygen-using partners may have shielded the oxygen-sensitive archaeon as life moved towards the oxygen-based lifestyle of most modern complex cells.

It builds on the team’s 2020 success in growing strain MK-D1, the first member of this group ever cultivated, from deep-sea sediment.

What happens next

The two cultures give researchers living models to study, rather than DNA sequences alone. The team plans to investigate how the cells are built and how they interact with their partners, to better understand how a simple archaeal cell gave rise to the complex cells of eukaryotes.

The study does not recreate the origin of complex life. It offers the clearest look yet at living relatives of the ancient archaeon that took part in that partnership.

Sources

• https://www.jamstec.go.jp/e/about/press_release/20261029/ (JAMSTEC, 29 October 2026)
• https://phys.org/news/2026-10-capturing-closest-archaeal-clues-eukaryotes.html (Phys.org, 29 October 2026)
• https://www.technology.org/2026/10/31/lab-grown-archaea-heimdallarchaeia-eukaryote-origins/ (Technology Org, 31 October 2026)

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