A recent discovery in Canada and Japan has raised big questions about what it means to be alive. The microbe Sukunaarchaeum mirabile is so tiny and needy that scientists are debating whether it’s truly a living organism. This tiny microbe relies heavily on an alive host to survive, blurring the lines between cellular life and viruses.
The National Human Genome Research Institute describes viruses as existing “near the boundary between the living and nonliving.” Viruses can’t function without interacting with a cell, but they’re essentially inert when alone. Sukunaarchaeum mirabile is different – it’s not a virus, but a highly streamlined cellular organism that challenges our understanding of life.
With one of the smallest genomes ever recorded, Sukunaarchaeum has reduced metabolic pathways and primarily encodes for DNA replication, transcription, and translation. This suggests an unprecedented level of dependence on a host, which raises questions about what defines minimal cellular life versus viruses.
Lead researcher Takuro Nakayama says that Sukunaarchaeum could be “the tip of the iceberg,” pointing to hidden diversity of life forms with ultra-reduced genomes. The discovery is challenging our understanding of cellular evolution and raises new perspectives on the definition of life, particularly in relation to metabolism.
Scientists agree that key features of life include cellular structure, replication ability, and metabolism. Sukunaarchaeum’s lack of metabolism makes it a fascinating case study in this ongoing discussion about the definition of life.
Source: https://eu.usatoday.com/story/news/nation/2025/07/06/microbe-raises-questions-about-life/84428810007