Nanoarchaeum equitans

Even C. regius's symbiotic cyanobacteria have one point nine million base pairs.

Previously, the smallest known archaeal genome was the one belonging to Nanoarchaeum equitans.

At four hundred ninety thousand base pairs, it's more than twice as long as the new one the researchers found.

They initially figured that this tiny genome, too large to be merely statistical noise, was an abbreviated piece of a much larger genome erroneously compiled by their software.