Sukunaarchaeum discovery reveals smallest known archaeal genome

An international research team, including scientists from the University of Nottingham and the University of Tsukuba, has identified a microorganism with the smallest archaeal genome ever discovered. Named Candidatus Sukunaarchaeum mirabile, the organism contains only 189 protein-coding genes, making its genome less than half the size of the previously known smallest archaeal genome.

Despite its minimal genetic makeup, Sukunaarchaeum retains the essential machinery required to replicate its DNA and produce proteins. However, it has lost nearly all genes necessary for producing its own energy and nutrients, indicating a heavy reliance on other organisms for survival. Researchers noted that approximately one-quarter of its genome consists of large membrane proteins with unknown functions, which may suggest a parasitic lifestyle.

The discovery was made through the genetic analysis of marine plankton. Because the organism is genetically distinct from all previously known archaea, researchers believe it may belong to a much larger, previously unnoticed group of microorganisms.