Aeonophiles: Can an individual microbial cell live for a million years?

In the past few decades, we have learned that a vast microbial ecosystem extends many kilometers into Earth’s subsurface that rivals surface life in terms of numbers of cells and impact they make on Earth systems. These ecosystems contain deep evolutionary branches on the tree of life that have never been cultured in a laboratory, suggesting that they could have capabilities that differ from those we’ve ever seen before. One of the strangest things about this vast unknown ecosystem is that it appears to be so slow-growing that individual cells can survive, without dividing for thousands of years or longer. Thus, they may be a new type of extremophile called an aeonophile, because it uses extraordinarily long periods of time to its evolutionary advantage.

• The evidence for aeonophiles.
• Evolutionary models for aeonophiles.
• Implications of aeonophiles.

It is an extraordinary thing to suggest that individual cells persist, while alive and metabolically active, in Earth’s subsurface for thousands to millions of years, but the evidence appears to support this extreme conclusion. Such organisms could be important for identifying general principles of extremely slow life, which could lead to strategies for combatting pathogens that evade antibiotics through slowing their metabolism. The genomes of these organisms may offer extremely stable enzymes for biotechnology.