NASA - NASA-funded astrobiology research has changed the fundamental knowledge about what comprises all known life on Earth.
Researchers conducting tests in the harsh environment of Mono Lake in California have discovered the first known microorganism on Earth able to thrive and reproduce using the toxic chemical arsenic. The microorganism substitutes arsenic for phosphorus in its cell components.
"The definition of life has just expanded," said Ed Weiler, NASA's associate administrator for the Science Mission Directorate at the agency's Headquarters in Washington. "As we pursue our efforts to seek signs of life in the solar system, we have to think more broadly, more diversely and consider life as we do not know it."
This finding of an alternative biochemistry makeup will alter biology textbooks and expand the scope of the search for life beyond Earth. The research is published in this week's edition of Science Express.
Carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur are the six basic building blocks of all known forms of life on Earth. Phosphorus is part of the chemical backbone of DNA and RNA, the structures that carry genetic instructions for life, and is considered an essential element for all living cells.
Phosphorus is a central component of the energy-carrying molecule in all cells (adenosine triphosphate) and also the phospholipids that form all cell membranes. Arsenic, which is chemically similar to phosphorus, is poisonous for most life on Earth. Arsenic disrupts metabolic pathways because chemically it behaves similarly to phosphate.
"We know that some microbes can breathe arsenic, but what we've found is a microbe doing something new -- building parts of itself out of arsenic," said Felisa Wolfe-Simon, a NASA Astrobiology Research Fellow in residence at the U.S. Geological Survey in Menlo Park, Calif., and the research team's lead scientist. "If something here on Earth can do something so unexpected, what else can life do that we haven't seen yet?"
The newly discovered microbe, strain GFAJ-1, is a member of a common group of bacteria, the Gammaproteobacteria. In the laboratory, the researchers successfully grew microbes from the lake on a diet that was very lean on phosphorus, but included generous helpings of arsenic. When researchers removed the phosphorus and replaced it with arsenic the microbes continued to grow. Subsequent analyses indicated that the arsenic was being used to produce the building blocks of new GFAJ-1 cells.
The key issue the researchers investigated was when the microbe was grown on arsenic did the arsenic actually became incorporated into the organisms' vital biochemical machinery, such as DNA, proteins and the cell membranes. A variety of sophisticated laboratory techniques was used to determine where the arsenic was incorporated.
The team chose to explore Mono Lake because of its unusual chemistry, especially its high salinity, high alkalinity, and high levels of arsenic. This chemistry is in part a result of Mono Lake's isolation from its sources of fresh water for 50 years.
The results of this study will inform ongoing research in many areas, including the study of Earth's evolution, organic chemistry, biogeochemical cycles, disease mitigation and Earth system research. These findings also will open up new frontiers in microbiology and other areas of research.
"The idea of alternative biochemistries for life is common in science fiction," said Carl Pilcher, director of the NASA Astrobiology Institute at the agency's Ames Research Center in Moffett Field, Calif. "Until now a life form using arsenic as a building block was only theoretical, but now we know such life exists in Mono Lake."
The research team included scientists from the U.S. Geological Survey, Arizona State University in Tempe, Ariz., Lawrence Livermore National Laboratory in Livermore, Calif., Duquesne University in Pittsburgh, Penn., and the Stanford Synchroton Radiation Lightsource in Menlo Park, Calif.
NASA's Astrobiology Program in Washington contributed funding for the research through its Exobiology and Evolutionary Biology program and the NASA Astrobiology Institute. NASA's Astrobiology Program supports research into the origin, evolution, distribution, and future of life on Earth.
Click for video
**********
Mono Lake bacteria build their DNA using arsenic
discovermagazine - Arsenic isn’t exactly something you want to eat. It has a deserved reputation as a powerful poison. It has been used as a murder weapon and it contaminates the drinking water of millions of people. It’s about as antagonistic to life as a chemical can get. But in California’s Mono Lake, Felisa Wolfe-Simon has discovered bacteria that not only shrug off arsenic’s toxic effects, but positively thrive on it. They can even incorporate the poisonous element into their proteins and DNA, using it in place of phosphorus.
Out of the hundred-plus elements in existence, life is mostly made up of just six: carbon, hydrogen, oxygen, nitrogen, sulphur and phosphorus. This elite clique is meant to be irreplaceable. But the Mono Lake bacteria may have broken their dependence on one of the group – phosphorus – by swapping it for arsenic. If that’s right, they would be the only known living things to do this.
The discovery is amazing, but it’s easy to go overboard with it. For example, this breathlessly hyperbolic piece, published last year, suggests that finding such bacteria would be “one of the most significant scientific discoveries of all time”. It would imply that “Mono Lake was home to a form of life biologically distinct from all other known life on Earth” and “strongly suggest that life got started on our planet not once, but at least twice”.
The results do nothing of the sort. For a start, the bacteria – a strain known as GFAJ-1 – don’t depend on arsenic. They still contain detectable levels of phosphorus in their molecules and they actually grow better on phosphorus if given the chance. It’s just that they might be able to do without this typically essential element – an extreme and impressive ability in itself.
Nor do the bacteria belong to a second branch of life on Earth – the so-called “shadow biosphere” that Wolfe-Simon talked about a year ago. When she studied the genes of these arsenic-lovers, she found that they belong to a group called the Oceanospirillales. They are no stranger to difficult diets. Bacteria from the same order are munching away at the oil that was spilled into the Gulf of Mexico earlier this year. The arsenic-based bacteria aren’t a parallel branch of life; they’re very much part of the same tree that the rest of us belong to.
That doesn’t, however, make them any less extraordinary.
Phosphorus helps to form the backbone of DNA and it’s a crucial part of ATP, the molecule that acts as a cell’s energy currency. Arsenic sits just below phosphorus in the periodic table. The two elements have such similar properties that arsenic can usurp the place of phosphorus in many chemical reactions. But arsenic is a poor understudy – when it stands in for phosphorus, it produces similar but less stable products. This partially explains why the element is so toxic. But the bacteria of Mono Lake have clearly found a way to cope with this.
They have every reason to do so. Mono Lake sits in a sealed basin close to California’s Yosemite National Park. With no outlet connecting it to other bodies of water, any chemicals flowing into the lake tend to stay there. As a result, the lake has built up some of the highest concentrations of arsenic on the planet. To survive here, bacteria have to be able to cope with the poison.
In 2008, Ronald Oremland (who was also involved in the latest study) discovered bacteria in Mono Lake that can fuel themselves on arsenic. Like plants, they can photosynthesise, creating their own food using the power of the sun. But where plants use water in this reaction, the bacteria used arsenic. Wolfe-Simon has taken these discoveries a step further, by showing that the bacteria are actually incorporating arsenic into their most important of molecules.
She took sediment from Mono Lake and added it to Petri dishes containing a soup of vitamins and other nutrients, but not a trace of phosphorus. She took samples from these dishes and added them to fresh ones, gradually diluting them to remove any phosphorus that might have stowed away onboard. And all the while, she added more and more arsenic.
Amazingly, bacteria still grew in the dishes. Wolfe-Simon isolated one of these arsenic-lovers – a strain called GFAJ-1. Using an extremely sensitive technique called ICP-MS that measures the concentrations of different elements, she showed that the cells of these bacteria did indeed contain large amounts of arsenic.
By giving the bacteria a mildly radioactive form of arsenic, Wolfe-Simon could also track where the element ended up in the cells. The answer: everywhere. There was arsenic in the bacteria’s proteins and in their fat molecules. It had replaced phosphorus in many important molecules including ATP and glucose (a sugar). It was even in their DNA, a conclusion that Wolfe-Simon backed up with a number of other techniques. All other life uses phosphorus to create the backbone of the famous double helix, but GFAJ-1’s DNA had a spine of arsenic.
It’s an amazing result, but even here, there is room for doubt. As mentioned, Wolfe-Simon still found a smidgen of phosphorus in the bacteria by the end of the experiment. The levels were so low that the bacteria shouldn’t have been able to grow but it’s still not clear how important this phosphorus fraction is. Would the bacteria have genuinely been able to survive if there was no phosphorus at all?
Nor is it clear if the arsenic-based molecules are part of the bacteria’s natural portfolio. Bear in mind that Wolfe-Simon cultured these extreme microbes using ever-increasing levels of arsenic. In doing so, she might have artificially selected for bacteria that can use arsenic in place of phosphorus, causing the denizens of Mono Lake to evolve new abilities (or overplay existing ones) under the extreme conditions of the experiment.
Other species can cope with arsenic too. Some switch on genes that give them resistance to arsenic poisoning, while others can even “breathe” using arsenate. But GFAJ-1 uses the element to an even greater extent. How does it manage?
Under the microscope, the bacteria become around 50% larger if they grow on arsenic compared to phosphorus, and they develop large internal compartments called vacuoles. These might be the key to their success. Wolfe-Simon thinks that the vacuoles could act as a safe haven for unstable arsenic-based molecules – they might contain chemicals that steady the molecules, and they might keep out water that would hasten their breakdown.
These are questions for future research. In the mean time, the angle being used to sell the story is that this might have implications for alien life. Of course, the results have nothing to do with aliens. If anything, they expand the possibilities of what alien life might look like. If bacteria on Earth can exist using a biochemistry that’s very different to that of other microbes, it stands to reason that aliens could do the same.
That hasn’t stopped the hype machine from rolling forward, fuelled by a public announcement from NASA, teasing a press conference about an “astrobiology discovery”. It’s a shame. In teasing their own press conference two days ahead of time, and refusing to budge on the embargo when the first information trickled in, NASA effectively muzzled everyone who knew about the actual story while allowing speculation to build to fever pitch.
That may, of course, be their intention. However, I can’t help but feel that the result will be a lot of disappointed people, who’ve been robbed of an opportunity to be excited about a genuinely interesting discovery.
***********
Arsenic-loving bacteria may help in hunt for alien life
BBC - The first organism able to substitute one of the six chemical elements crucial to life has been found.
The bacterium, found in a California lake, uses the usually poisonous element arsenic in place of phosphorus.
The find, described in Science, gives weight to the long-standing idea that life on other planets may have a radically different chemical makeup.
It also has implications for the way life arose on Earth - and how many times it may have done so.
The "extremophile" bacteria were found in a briny lake in eastern California in the US.
While bacteria have been found in inhospitable environments and can consume what other life finds poisonous, this bacterial strain has actually taken arsenic on board in its cellular machinery.
Until now, the idea has been that life on Earth must be composed of at least the six elements carbon, hydrogen, oxygen, nitrogen, sulphur and phosphorus - no example had ever been found that violates this golden rule of biochemistry.
The bacteria were found as part of a hunt for life forms radically different from those we know.
"At the moment we have no idea if life is just a freak, bizarre accident which is confined to Earth or whether it is a natural part of a fundamentally biofriendly universe in which life pops up wherever there are Earth-like conditions," explained Paul Davies, the Arizona State University and Nasa Astrobiology Institute researcher who co-authored the research.
"Although it is fashionable to support the latter view, we have zero evidence in favour of it," he told BBC News.
"If that is the case then life should've started many times on Earth - so perhaps there's a 'shadow biosphere' all around us and we've overlooked it because it doesn't look terribly remarkable."
Proof of that idea could come in the form of organisms on Earth that break the "golden rules" of biochemistry - in effect, finding life that evolved separately from our own lineage.
Study lead author Felisa Wolfe-Simon and her colleagues Professor Davies and Ariel Anbar of Arizona State University initially suggested in a paper an alternative scheme to life as we know it.
Their idea was that there might be life in which the normally poisonous element arsenic (in particular as chemical groups known as arsenates) could work in place of phosphorus and phosphates.
Putting it to the test, the three authors teamed up with a number of collaborators and began to study the bacteria that live in Mono Lake in California, home to arsenic-rich waters.
The researchers began to grow the bacteria in a laboratory on a diet of increasing levels of arsenic, finding to their surprise that the microbes eventually fully took up the element, even incorporating it into the phosphate groups that cling to the bacteria's DNA.
Notably, the research found that the bacteria thrived best in a phosphorus environment.
That probably means that the bacteria, while a striking first for science, are not a sign of a "second genesis" of life on Earth, adapted specifically to work best with arsenic in place of phosphorus.
However, Professor Davies said, the fact that an organism that breaks such a perceived cardinal rule of life makes it is a promising step forward.
"This is just a weird branch on the known tree of life," said Professor Davies. "We're interested ultimately in finding a different tree of life... that will be the thing that will have massive implications in the search for life in the Universe.
"The take-home message is: who knows what else is there? We've only scratched the surface of the microbial realm."
John Elliott, a Leeds Metropolitan University researcher who is a veteran of the UK's search for extraterestrial life, called the find a "major discovery".
"It starts to show life can survive outside the traditional truths and universals that we thought you have to use... this is knocking one brick out of that wall," he said.
"The general consensus is that this really could still be an evolutionary adapatation rather than a second genesis. But it's early days, within about the first year of this project; it's certainly one to think on and keep looking for that second genesis, because you've almost immediately found an example of something that's new."
Simon Conway Morris of the University of Cambridge agreed that, whatever its implications for extraterrestrial life, the find was significant for what we understand about life on Earth.
"The bacteria is effectively painted by the investigators into an 'arsenic corner', so what it certainly shows is the astonishing and perhaps under-appreciated versatility of life," he told BBC News.
"It opens some really exciting prospects as to both un-appreciated metabolic versatility... and prompting the questions as to the possible element inventory of remote Earth-like planets".
Send us an email
New Items - Strickler's Celebrity Autographs
ANOMALIST BOOKS
Works on maverick science, unexplained mysteries, unorthodox theories, strange talents, and unexpected discoveries. Please check out their excellent and diverse catalog
The 'C' Influence
Actualizing Esoteric Discussion
"The latest news from beyond the mainstream"
Join Ben & Aaron for their weekly podcast!
Check out Mysterious Universe Plus+ all access format!
Spirit Rescue International
Providing no-cost professional spiritual help, personal support and guidance
Take the first step towards genuine peace of mind
Phantoms & Monsters Wiki
A NETWORK OF INVESTIGATORS, ENTHUSIASTS AND THOSE SEEKING THE TRUTH
THROUGH PARANORMAL EDUCATION AND DISCUSSION
Astral Perceptions - Discussion of interterrestrial and multidimensional phenomena including
conversations on the proficiency of remote viewing
SUPPLY BASE
Buy alternative supplies and gifts
CLICK HERE!
