Smallest-Ever Archaeal Genome Found: 189 Proteins, Fewer Than Many Viruses

Researchers described Candidatus Sukunaarchaeum mirabile, an archaeon with the smallest known genome at 238,034 base pairs encoding just 189 proteins. The cell keeps its own ribosomes but has lost all metabolism and depends entirely on a host.

• Sukunaarchaeum's genome is 238,034 base pairs and 189 proteins, 51% smaller than the previous record-holder Nanoarchaeum equitans
• 52% of its proteins handle genetic information processing; no metabolic pathways remain
• The cell retains ribosomes and 31 tRNA genes but relies on the dinoflagellate host Citharistes regius
• Findings were verified with Illumina and Oxford Nanopore sequencing and published in Current Biology