Could ancient bacteria hold the secret to survival?
31 August 2007
What's the secret to living a long life? Scientists could soon reveal the answer after discovering the oldest living organism ever found - a half-million-year-old, ice-dwelling kind of bacteria.
Antenna digs deeper...
Image: istockphoto.com/Carbon Lotus
Scientists have known for a while that bacteria are some of the most elderly organisms on Earth. But until now they thought the bugs spent most of this super lifespan 'switched off', saving themselves for optimum living conditions.
But new findings, published in the journal Proceedings of the National Academy of Sciences, show that some bacteria can stay switched on and going strong for much longer than previously thought possible.
This bacteria belong to a group named Arthrobacter, the most common type found in the ancient bacteria samples.
Image: T Tamura/T Nishii/K Hatano
Now scientists hope that these resilient bugs will shed light on the ageing process, and that they could even tell us how life might survive on Mars and other icy planets.
How did the scientists unearth their find?
The international team of researchers drilled out samples of frozen soil from Antarctica, Siberia and northern Canada and took them back to their lab to test for signs of life. They found DNA from many of different types of bacteria, but only some of them were still alive.
The temperature of this 'permafrost' soil is about minus 20 degrees Celsius. It's been completely frozen for almost 600,000 years.
Image: Thomas Gilbert
How did the scientists work this out?
When organisms die their DNA starts to break down, so scientists usually find there is a build-up of harmful mutations over time. But the DNA of these bacteria was still intact and healthy.
To double-check their findings, the team also tested whether their bacteria were still active. They found that the bugs were still 'breathing' and giving off tiny amounts of carbon dioxide, even though their metabolisms had slowed right down in the cold.
This is a close up of a permafrost sample that the scientists tested out in their lab.
Image: Tom Gilbert
'These bacteria are clearly still alive and actively repairing their DNA over time,' explains team member Thomas Gilbert of the University of Copenhagen. 'But they've managed to slow their metabolisms right down. This may even be their normal strategy for life.'
Thomas Gilbert of the University of Copenhagen was one of the team who carried out this research.
Image: Thomas Gilbert
'This is a really interesting finding,' says Enrico Cappellini, an expert in ancient DNA at the University of York. 'It proves that organisms can remain viable for a very long time. Now further work needs to be done to support these early results.
'I think this is just the beginning,' Enrico adds. 'The next step might be to try and understand the biological mechanisms and physiology behind this to work out exactly how the bacteria are surviving this long - this could be really exciting.'
Enrico Cappellini, the PALEO team, University of York.
Image: University of York
Thomas agrees. 'DNA repair is very complicated, but it would be fascinating to see how they're surviving down there for so long. We know that the colder you make the environment, the longer DNA survives - the question is "What's the longest DNA can survive?" This has implications for life in other extreme environments and other planets too.
'An environment like Mars is very, very cold, so if there was life on Mars a long time ago we might still find traces of it now. And more exciting, there may even be ancient life like these bacteria that are still alive there today. But this is all still just guesswork.'
Mars is covered in ice at its poles which could be harbouring life even now.
Image: NASA
We may not yet know all these bacteria's secrets, but one thing's for sure. These tiny bugs have given scientists a lot to think about.