Tiny Lord of the Plankton Sets Record for Smallest Genome Among Its Kind

THE OPEN OCEAN — An international team of researchers has identified a microscopic organism whose genome is the smallest yet reported for any member of the archaea, according to a report in The Debrief. The findings were published in the journal Current Biology by a group that includes researchers from the University of Nottingham and the University of Tsukuba.

The organism was found during genetic sequencing of individual marine plankton. It has been provisionally named Candidatus Sukunaarchaeum mirabile, after Sukunabikona, a deity of Japanese mythology whose name the article translates as "renowned little lord". The god is described as a dwarf about the size of a human thumb, and as a patron of healing, hot springs and magic.

The genome is said to be less than half the size of the smallest archaeal genome previously known and holds just 189 protein-coding genes. Genetic analysis indicates the creature belongs to no recognized archaeal group, while related sequences in marine samples hint at a broader, overlooked lineage.

The creature has apparently discarded nearly all the genes needed to make its own nutrients and energy, yet kept the machinery for copying its genome and making proteins. Professor Thorsten Allers of Nottingham, a co-author, says this suggests it may be near the minimum genetic information an independent cell requires.

About a quarter of the genome encodes unusually large membrane proteins of unclear function. Similar proteins occur in parasitic archaea, so the researchers suspect a parasitic life, though no host has been identified.

Notably, no one has yet viewed the organism under a microscope, and it has not been cultured, hence the provisional name. The team's next steps are to find where it lives, what feeds it, and how it deals with any host.