The world’s oldest bacteria

Willerslev collecting soil samples

in the permafrost in the Yukon,
Canada (Credit: Duane Froese)

A research has for the first time ever discovered DNA from living bacteria that are more than half a million years old. Never before has traces of still living organisms that old been found. The exceptional discovery can lead to a better understanding of the ageing of cells and might even cast light on the question of life on Mars.

The discovery is being published in the current issue of PNAS (Proceedings of The National Academy of Sciences of The United States of America). The discovery was made by Professor Eske Willerslev from the University of Copenhagen and his international rearch team.

How cells age

All cells decompose with time. But some cells are better than others to postpone the decomposing and thus delay ageing and eventually death. And there are even organisms that are capable of regenerating and thereby repair damaged cells. These cells – their DNA – are very interesting to the understanding of the process of how cells break down and age.

Oldest life on earth

The research team, which consists of internatinal experts in, among other things, DNA-traces in sediments and organisms, have found ancient bacteria that still contains active and living DNA. So far, it is the oldest finding of organisms containing active DNA and thus life on this earth. The discovery was made after excavations of layers of permafrost in the nort-western Canada, the north-eastern Sibiria and Antarctica.

- Our project is about eg. examining how bacteria can live after having been frozen down for millions of years. Other researchers has tried to uncover the life of the past and the following evolutionary development by focusing on cells that are in a state of deadlike lethargy. We, on the other hand, have found a method that makes is possible to extract and isolate DNA-traces from cells that are still active. It gives a more precise picture of the past life and the evolution towards the present because we are dealing with cells that still have a metabolistic function – unlike “dead” cells where that function has ceased, says Eske Willerslev.

Future perspectives

After the fieldwork and the isolation of the DNA, the researchers compared the DNA to DNA from a worldwide gene-bank in the US to identify the ancient material. Much in the same way the police compares fingerprints from a crime. The researchers were able to place the DNA more precisely and to place it in a context.

- There is a very long way, of course, from our basic research towards understanding why some cells can become that old. But it is interesting in this context to look at how cells break down and are restored and thus are kept over a very long period. Our methods and results can be used to determine if there was ever life on Mars the way we perceive life on earth. And then there is the grand perspective in relation to Darwin’s evolution theory. It predicts that life never returns to the same genetic level. But our findings allow us to post the question: are we dealing with a circular evolution where development, so to speak, bites its own tail if and when ancient DNA are mixed with new?, says Eske Willerslev.

The research team:

Professor Eske Willerslev

University of Copenhagen

Sarah Stewart Johnson
Massachusetts Institute of Technology

Martin B. Hebsgaard
University of Copenhagen

Torben R. Christensen
Lund University

Mikhail Mastepanov
Lund University

Rasmus Nielsen
University of Copenhagen

Kasper Munch
University of Copenhagen

Tina B. Brand
University of Copenhagen

M. Thomas P. Gilbert
University of Copenhagen

Maria T. Zuber
Massachusetts Institute of Technology

Michael Bunce
Murdoch University

Regin Rønn, University of Copenhagen

David Gilichinsky
Russian Academy of Sciences

Duane Froese
University of Alberta

SOURCE : University of Copenhagen