The smallest genome ever found: a microbe with 189 genes redraws the edge of life

Scientists analyzing the genetic material of individual ocean-plankton microbes have found a previously unknown organism, Candidatus Sukunaarchaeum mirabile — named for a small Japanese deity — carrying the smallest genome ever recorded: just 238,034 base pairs encoding 189 proteins, less than half the size of the previous smallest archaeal genome. Remarkably, it keeps the machinery to copy its own DNA and make proteins, yet has lost nearly all genes for producing its own nutrients and energy, surviving as a dependent of its host. The international team, including researchers from the University of Tsukuba and the University of Nottingham, published the findings in Current Biology on October 9.