Forget aliens, meet the 'INTRAterrestrials': Strange new viruses discovered beneath the ocean floor

• New archeal virus infects primitive bacteria living off methane underground
• The virus has genes that speed up its own mutation rate helping it to adapt
• Scientists believe it holds the key to life surviving in extreme environments
• They discovered the virus in samples taken from beneath the Santa Monica Basin off the coast of California but say the viruses live around the world

Those hoping to meet an alien creature may well do better to look beneath the waves than beyond our own atmosphere.

Scientists have discovered strange new organisms that infect the primitive forms of life that live deep below the ocean floor.

While examining species of bacteria that thrive on the fossil fuel deposits deep inside the Earth - known as archae - they have found a new type of virus that infects them.

This graphic shows how the new archael virus changes uses 'docking tips' - purple area - to infect bacteria

They now believe it may be viruses like this that actually hold the secret that have allowed archae bacteria to adapt to some of the harshest environments on Earth.

This is because the virus actively causes one of its own genes to mutate - allowing it to develop new ways of coping with the ecosystem it finds itself in.

BACTERIA THAT SURVIVE ON COAL

Life has been discovered nearly a mile and half underground, raising hopes bacteria might be able to survive deep beneath the surface of other planets.

Researchers found the single-celled organisms living inside coal beds more than 8,000ft (2,440 metres) below the seabed off the coast of Japan. It is the deepest life has yet been found beneath the ocean.

At those depths the spherical microbes have to survive huge pressures that would crush most organisms while having no access to light or oxygen often needed for life.

Instead, the bacteria scavenge the chemicals they need to survive by breaking down the hydrocarbon compounds in the coal around them. 

The findings have raised the prospect that life may still be clinging on deep underground on planets such as Mars, where there was once thought to be flowing water on the surface.

Scientists have already speculated that the discovery of archae bacteria deep inside the Earth's crust has raised prospects of finding life on other planets.

Now it seems they may also find viruses like this one living there too.

Dr David Valentine, a geoscientist at the University of California Santa Barbara and co-author of the research, said: 'Our study uncovers mechanisms by which viruses and archaea can adapt in this hostile environment.'

Dr Valentine and his colleagues discovered the virus while exploring methane vents 2,800 feet beneath the surface of the ocean in the Santa Monica basin off the coast of California.

By pushing tubes into the ocean floor they retrieved sediments and brought the contents back to the lab where they grew the bacteria.

When they screened the genomes of the methane-eating bacteria they discovered the genetic fingerprint of the new virus.

The researchers, whose work is published in the journal Nature Communications, screened other samples taken from around the world and found similar fingerprints in bacteria from Norway and elsewhere along the coast of California.

Dr Blair Paul, lead author of the research and an earth scientist at the University of California Santa Barbara, said: 'The evidence suggests that this viral type is distributed around the globe in deep ocean methane seeps.'

Scientists used submersible Alvin (left) to obtain sediment samples (right) from the Santa Monica basin

The sea floor, shown above, is covered in microbial mats of primitive bacteria that are infected with viruses

The researchers also found that a small genetic element - known as a diversity-generating retroelement - was able to accelerate mutation of a specific part of the virus's own genome.

'But the ability to mutate those tips is an offensive countermeasure against the cell's defenses, a move that resembles a molecular arms race.'

The researchers also found similar guided mutation elements in the archae bacteria living under the ocean floor themselves. Tiny bacteria known as nanoarchaea targetted four distinct genes.

Dr Valentine said: 'The cell is choosing to modify certain proteins.

The image above shows a ridge covered in microbial mats on the ocean floor of the Santa Monica basin

'It's doing its own protein engineering. While we don't yet know what those proteins are being used for, learning about the process can tell us something about the environment in which these organisms thrive.'

The findings suggest that life living beneath the ocean floor and in the cracks of rocks deep below the surface could be far more diverse than previously thought.

It is thought that there may even be more biomass living inside the Earth than on its surface.

Matt Kane, program director for the National Science Foundation's Division of Environmental Biology, said: 'Life far beneath the Earth's subsurface is an enigma.

'By probing deep into our planet, these scientists have discovered new information about Earth's microbes and how they evolve.'