Science grapples with the concept that alien life may be among us

It is life, but not as we know it. The first life form on Earth to use deadly arsenic as one of its chemical building blocks has been discovered in a desert lake in California.

The find has astonished biologists who had believed that it was impossible for arsenic, normally considered a poison, to be used as building material for biological molecules such as DNA and proteins.

Scientists said last night that the discovery widens the scope for finding "weird" forms of extraterrestrial life on other planets that would have been considered – until now – to be too inhospitable for living organisms to evolve. For decades it has been accepted dogma in biology that all life on Earth, from the tiniest microbe to the biggest blue whale, relies on the same six chemical elements as the fundamental building blocks of biological molecules.

It was thought that the same principle must hold true for any extraterrestrial life forms living on other planets, which narrowed the search for habitable places where life could evolve.

Now, researchers in the United States, including Nasa-funded astrobiologists involved in the search for extraterrestrial life in space, have added the element arsenic to the list of six involved in the chemistry of life: oxygen, carbon, hydrogen, nitrogen, phosphorus and sulphur .

The arsenic-using microbe is known only by its code name, GFAJ-1, and was extracted from the muddy sediments of California's Mono Lake, which is naturally salty with high concentrations of arsenic.

Tests have demonstrated that the bacterium uses arsenic as a substitute for phosphorus, which is a neighbouring element on the Periodic Table and shares similar properties.

Although it grows better in a phosphorus-rich environment, the microbe appears happy to use arsenic when necessary in the form of arsenate, a molecule formed with oxygen that acts as a substitute for phosphate, the scientists said. Felisa Wolfe-Simon, of the Nasa Astrobiology Institute and US Geological Survey at Menlo Park, California, said: "Our findings are a reminder that life as we know it could be much more flexible than we generally assume or can imagine.

"Yet, this story isn't about arsenic or Mono Lake. If something here on Earth can do something so unexpected, what else can life do that we haven't seen yet?"



The study, published in the journal Science, reports that arsenic in the form of arsenate can make the appropriate chemical bonds with carbon and oxygen to act as a substitute for the phosphate molecule normally found in DNA and other biological molecules.

The scientists said that sophisticated analytical techniques have shown that the arsenic was incorporated into proteins, lipids, nucleic acids and other vital molecules found inside living cells. Arsenic was not simply an innocent bystander but an active element in the life-giving processes of the cell.

The discovery has vindicated a hypothesis that Dr Wolf-Simon put forward at a scientific meeting in 2006 when she suggested that primitive life forms in the early evolution of life on Earth may have used arsenic, and that similar microbes may still exist in some extreme environments.

"Such organisms could have evolved on the ancient Earth and might persist in unusual environments today," Dr Wolf-Simon said.

Suggested Topics
Start your day with The Independent, sign up for daily news emails
PROMOTED VIDEO
Life and Style
Suited and booted in the Lanvin show at the Paris menswear collections
fashionParis Fashion Week
News
i100
Arts and Entertainment
Kara Tointon and Jeremy Piven star in Mr Selfridge
tvActress Kara Tointon on what to expect from Series 3
Voices
Winston Churchill, then prime minister, outside No 10 in June 1943
voicesA C Benson called him 'a horrid little fellow', George Orwell would have shot him, but what a giant he seems now, says DJ Taylor
News
i100
News
An asteroid is set to pass so close to Earth it will be visible with binoculars
news
News
ebooks
ebooksA year of political gossip, levity and intrigue from the sharpest pen in Westminster
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Austen Lloyd: Private Client Solicitor - Oxford

Excellent Salary : Austen Lloyd: OXFORD - REGIONAL FIRM - An excellent opportu...

Austen Lloyd: Clinical Negligence Associate / Partner - Bristol

Super Package: Austen Lloyd: BRISTOL - SENIOR CLINICAL NEGLIGENCE - An outstan...

Recruitment Genius: Sales Consultant - Solar Energy - OTE £50,000

£15000 - £50000 per annum: Recruitment Genius: Fantastic opportunities are ava...

Recruitment Genius: Compute Engineer

Negotiable: Recruitment Genius: A Compute Engineer is required to join a globa...

Day In a Page

Syria crisis: Celebrities call on David Cameron to take more refugees as one young mother tells of torture by Assad regime

Celebrities call on David Cameron to take more Syrian refugees

One young mother tells of torture by Assad regime
The enemy within: People who hear voices in their heads are being encouraged to talk back – with promising results

The enemy within

People who hear voices in their heads are being encouraged to talk back
'In Auschwitz you got used to anything'

'In Auschwitz you got used to anything'

Survivors of the Nazi concentration camp remember its horror, 70 years on
Autumn/winter menswear 2015: The uniforms that make up modern life come to the fore

Autumn/winter menswear 2015

The uniforms that make up modern life come to the fore
'I'm gay, and plan to fight military homophobia'

'I'm gay, and plan to fight military homophobia'

Army general planning to come out
Iraq invasion 2003: The bloody warnings six wise men gave to Tony Blair as he prepared to launch poorly planned campaign

What the six wise men told Tony Blair

Months before the invasion of Iraq in 2003, experts sought to warn the PM about his plans. Here, four of them recall that day
25 years of The Independent on Sunday: The stories, the writers and the changes over the last quarter of a century

25 years of The Independent on Sunday

The stories, the writers and the changes over the last quarter of a century
Homeless Veterans appeal: 'Really caring is a dangerous emotion in this kind of work'

Homeless Veterans appeal

As head of The Soldiers' Charity, Martin Rutledge has to temper compassion with realism. He tells Chris Green how his Army career prepared him
Wu-Tang Clan and The Sexual Objects offer fans a chance to own the only copies of their latest albums

Smash hit go under the hammer

It's nice to pick up a new record once in a while, but the purchasers of two latest releases can go a step further - by buying the only copy
Geeks who rocked the world: Documentary looks back at origins of the computer-games industry

The geeks who rocked the world

A new documentary looks back at origins of the computer-games industry
Belle & Sebastian interview: Stuart Murdoch reveals how the band is taking a new direction

Belle & Sebastian is taking a new direction

Twenty years ago, Belle & Sebastian was a fey indie band from Glasgow. It still is – except today, as prime mover Stuart Murdoch admits, it has a global cult following, from Hollywood to South Korea
America: Land of the free, home of the political dynasty

America: Land of the free, home of the political dynasty

These days in the US things are pretty much stuck where they are, both in politics and society at large, says Rupert Cornwell
A graphic history of US civil rights – in comic book form

A graphic history of US civil rights – in comic book form

A veteran of the Fifties campaigns is inspiring a new generation of activists
Winston Churchill: the enigma of a British hero

Winston Churchill: the enigma of a British hero

A C Benson called him 'a horrid little fellow', George Orwell would have shot him, but what a giant he seems now, says DJ Taylor
Growing mussels: Precious freshwater shellfish are thriving in a unique green project

Growing mussels

Precious freshwater shellfish are thriving in a unique green project