How on earth did the Mono Lake arsenic eating microbes discovered by Felisa Wolfe-Simon go (presumably) from eating phosphorus and utilizing phosphorus in their DNA to eating arsenic and utilizing arsenic in their DNA? This is far more than just another extremophile organism liking a difficult environment. This is an organism that appears to have switched out phosphorus for arsenic as a building block in its DNA—something that biologists previously thought highly implausible (at best). This is an organism, in other words, that has figured out how to become what it eats. It’s as if we, as humans, started eating iron ore and didn’t just pass it through our guts, but became creatures, over time, that run on iron ore, swapping out, say, our carbon atoms for iron atoms in our DNA. These Mono Lake organisms are literally swapping out phosphorus atoms for arsenic atoms in their DNA. Here’s the New York Times:
Felisa Wolfe-Simon, a NASA astrobiology fellow at the United States Geological Survey in Menlo Park, Calif., who led the experiment, said, “This is a microbe that has solved the problem of how to live in a different way.” This story is not about Mono Lake or arsenic, she said, but about “cracking open the door and finding that what we think are fixed constants of life are not.” Dr. Wolfe-Simon and her colleagues publish their findings Friday in Science. Caleb Scharf, an astrobiologist at Columbia University who was not part of the research, said he was amazed. “It’s like if you or I morphed into fully functioning cyborgs after being thrown into a room of electronic scrap with nothing to eat,” he said.
Caleb Scharf’s comment is mind blowing: talk about life making a way! And it is Scharf’s comment above, and not Felisa Wolfe-Simon’s, that most dramatically conveys what this discovery means. Somehow these organisms are not just deriving energy from a conventionally extreme source. They are becoming the source. It’s as if plants didn’t just utilize light for energy in photosynthesis, but became light beings. And it’s as if human beings didn’t just use iron to move oxygen around their bodies, but incorporated iron into their DNA, becoming iron-based beings. Here’s the New York Times again:
Phosphorus is one of six chemical elements that have long been thought to be essential for all Life As We Know It. The others are carbon, oxygen, nitrogen, hydrogen and sulfur. While nature has been able to engineer substitutes for some of the other elements that exist in trace amounts for specialized purposes — like iron to carry oxygen — until now there has been no substitute for the basic six elements. Now, scientists say, these results will stimulate a lot of work on what other chemical replacements might be possible.
The bacterium, scraped from the bottom of Mono Lake in California and grown for months in a lab mixture containing arsenic, gradually swapped out atoms of phosphorus in its little body for atoms of arsenic.
Swapping out the atoms of phosphorus for the atoms of arsenic in their DNA, and not just utilizing them within the confines of the six essential building blocks of life—phosphorus, carbon, oxygen, nitrogen, hydrogen and sulfur—is what makes this discovery shocking (and makes life on other worlds, including those radically different from our own, more plausible). There is, however, an important qualification toward the end of the New York Times’ report on this:
A bacterium known as strain GFAJ-1 . . . proved to grow the best of the microbes from the lake, although not without changes from their normal development. The cells grown in the arsenic came out about 60 percent larger than cells grown with phosphorus, but with large, empty internal spaces. By labeling the arsenic with radioactivity, the researchers were able to conclude that arsenic atoms had taken up position in the microbe’s DNA as well as in other molecules within it. Dr. Joyce, however, said that the experimenters had yet to provide a “smoking gun” that there was arsenic in the backbone of working DNA.
In other words, the arsenic is being incorporated into the DNA, but the researchers have not yet conclusively demonstrated that the organism’s “backbone” of DNA—that is, its normally phosphorus backbone—is actually functioning as an arsenic backbone. Here’s how the New York Times characterizes the “backbone” of DNA:
Phosphorus chains form the backbone of DNA and its chemical bonds, particularly in a molecule known as adenosine triphosphate, the principal means by which biological creatures store energy. “It’s like a little battery that carries chemical energy within cells,” said Dr. Scharf. So important are these “batteries,” Dr. Scharf said, that the temperature at which they break down, about 160 Celsius (320 Fahrenheit), is considered the high-temperature limit for life.
The bottom line is this: we have an organism on our planet right now that astrobiologists can study that has apparently found a building block for sustaining life that is different from every other organism on our planet: it is not (primarily) a phosphorus utilizing organism—as we all are—but an arsenic utilizing organism; and its DNA may not run with a phosphorus backbone (as, again, ours does), but an arsenic one. If there are arsenic laden worlds out there with bacterial life on them, they are likely to have creatures there that are like this bacteria discovered at Mono Lake. It is as if we scooped up a mud dwelling organism from another world, brought it to earth, and now have it right here, at this very moment, to research.
Isn’t that an imagination fire starter? It means, for purposes of study, that we really do have an alien life form in our midst. It is not using, for its life, a building block central to our own life (phosphorus), but one poisonous to it (arsenic).
And if I’m understanding this BBC documentary tease clip correctly, Felisa Wolfe-Simon is suggesting that the organism must be vastly old, not something that recently evolved in Mono Lake itself over the past million years (Mono Lake is about one million years old). This organism, in other words, is probably a “living fossil” from a time in earth’s history when life was only just starting. Somehow, this particular organism has managed to keep itself around, in precarious arsenic niches, for perhaps billions of years. Or maybe it was seeded here from elsewhere—from space. Hmm.
Calling this something alien is no exaggeration.