A team of scientists from Dalhousie University has discovered a microbe that challenges our traditional understanding of life. Sukunaarchaeum mirabile is an organism that is undeniably cellular but retains many genes typically associated with viruses. Its genome fits into 238,000 base pairs and is profoundly stripped-down, lacking virtually all recognizable metabolic pathways.
Unlike viruses, which can be both large and small, Sukunaarchaeum has a full toolkit for protein synthesis, but only uses its replicative core. The team calls it a “cellular entity retaining only its replicative core.” This means that the microbe relies on its host cell for nearly everything else it needs to stay alive.
Phylogenetic trees place Sukunaarchaeum on a deep branch within the Archaea domain, suggesting that it may be a new phylum. The team proposes creating a new phylum to accommodate this organism’s unique characteristics.
The discovery raises questions about what constitutes life and how we define the boundaries between living organisms. It also highlights the need for updated biosecurity protocols to screen for all types of symbiotic parasites, not just free-living microbes.
Sukunaarchaeum may hold clues for synthetic biology groups pursuing engineered minimal cells. The microbe’s extreme genome pruning could have evolved as a result of its host environment providing nutrients, allowing redundant pathways to decay.
The study provides a glimpse into early evolution and the potential for ancient lifestyle patterns to shape modern-day organisms. Further research is needed to investigate whether similar organisms exist in other marine ecosystems or symbiotic relationships.
Source: https://www.earth.com/news/scientists-discover-an-organism-that-defies-the-definition-of-life-sukunaarchaeum