Weird place on Earth Mono Lake in eastern California is where researchers found a type of bacteria that appears to break the rules for how we think life should survive. Credit: NASA image gallery

You may not know phosphorus when you see it, but your body does. Phosphorus is a sturdy workhorse element. In DNA molecules, phosphorus helps support the whole double helix. Within cells, energy shows up as ATP — and the “P” stands for phosphorus (specifically, phosphate, a form of phosphorus).

All life as we know it, in other words, depends on phosphorus. For that reason, scientists around the world were shocked December 2 when a team of scientists announced finding life forms that didn’t necessarily depend on this all-important element. In laboratory tests, the scientists grew bacteria that were able to use arsenic — a different element with similar chemistry — in the place of phosphorus.

It’s a surprising discovery because living organisms have never been found without all six of the ingredients crucial to life: carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur (all together known as CHNOPS). Arsenic, though, is a potentially fatal poison.

Many scientists say they would like to see more evidence that the research team did in fact observe life forms using arsenic instead of phosphorus.

“This is an amazing result, a striking, very important and astonishing result — if true,” Alan Schwartz told Science News. Schwartz researches chemistry at Radboud University Nijmegen in the Netherlands. “I’m even more skeptical than usual, because of the implications. But it is fascinating work.”

The bacteria came from Mono Lake, a lake in eastern California that is well known for its unusual population of living organisms, including shrimp and algae. The lake doesn’t drain, so the only way for water to leave is through evaporation. As a result, the lake is much saltier than the ocean.

An up-close picture of the bacteria GFAJ-1 grown on arsenic. Credit: Jodi Switzer Blum, NASA

Several researchers had been studying a number of tiny organisms that lived in Mono Lake mud. Astrobiologists study life in the universe and want to know how it started, how it has changed, and what will happen to life in the future. They also want to know whether life exists on other planets and if so, what it might look like. Many astrobiologists study what lives in Earth’s strangest places, such as Mono Lake, as a way to understand the possibilities for life.

The study was led by Felisa Wolfe-Simon of NASA’s Astrobiology Institute and the U.S. Geological Survey in Menlo Park, Calif. She and her team removed organisms from the Mono samples and grew those bacteria in the lab. The scientists fed the microbes with sugar and vitamins — but left out phosphate. Then they changed the diet again, and gave the microbes arsenate, which is a form of arsenic.

In one type of bacteria, called GFAJ-1, the researchers observed that arsenic wasn’t fatal. The bacteria continued to grow, though not as fast as if they’d had phosphorus. After studying these bacteria, Wolfe-Simon and her team concluded that the organisms had begun to make use of the arsenic the way they usually used phosphorus. The researchers suggest that arsenic was being used as a building block in the bacteria’s DNA.

“This microbe, if we are correct, has solved the challenge of being alive in a different way,” Wolfe-Simon told Science News.

If the scientists are right, then “life as we know it” may not include all the life that actually is possible. For astrobiologists, that conclusion suggests that life on other planets may not necessarily look like life on Earth.

It’s possible that follow-up studies will show that the researchers were mistaken. Wolfe-Simon and her team could not get rid of all the phosphorus when they were growing the bacteria. Some scientists say minute amounts might be enough to keep the microbes alive. It’s possible that, in the experiment, the bacterium GFAJ-1 was still getting small amounts of phosphate.

Can life exist using poison instead of phosphorus? Life of a different type is an exciting prospect, so stay tuned to see how the scientific community reacts. Next up, scientists will want to know how, exactly, the arsenic substitution works.

POWER WORDS

arsenic A highly poisonous metallic element having three allotropic forms, yellow, black and gray, of which the brittle, crystalline gray is the most common. Used in insecticides.

phosphorus A highly reactive, nonmetallic element occurring naturally in phosphates.

DNA A nucleic acid that carries the genetic information in the cell. DNA consists of two long chains of nucleotides twisted into a double helix and joined by hydrogen bonds between the bases.

molecule A group of like or of different atoms held together by chemical forces.

microbe A minute life form; a microorganism, especially a bacterium that causes disease.

bacterium A life form that is a single cell and too small to see without using a microscope. Bacteria (plural of bacterium) live in almost every environment on Earth, including very cold places, very warm places, in all types of water, in the air, even on and in plants and animals. These microorganisms can also cause disease in plants and animals.

Until now, all the digging has happened only in Earth’s outer layer, called the crust. Oil and gas wells normally go no deeper than about 6 kilometers. A new study shows that natural gas, mainly methane, may also form in a much deeper layer called the mantle. This means that new sources of energy could lie at depths of 100 kilometers (62 miles) or more.

During a simulation of the conditions in Earth’s mantle, this bubble of methane formed when researchers mixed iron oxide, calcite, and water at high temperatures and pressures.

PNAS

Oil and gas found near Earth’s surface are often described as fossil fuels. Most scientists favor the idea that these hydrocarbon fuels were formed by the breakdown of ancient plants and animals. However, recent research also shows that methane gas can form in the crust when there are no living creatures around.

Researchers from Indiana University South Bend wondered if this could also happen deeper down. So they did a lab experiment to simulate conditions in the mantle. They combined materials normally found at those depths. Then they put the mixture under extreme heat and pressure.

The experiment produced tiny bubbles of methane gas, the scientists report. However, no one knows yet how much methane, if any, is actually present in the mantle. And, if it is present, whether any gas might seep up into the crust and emerge from spots on the ocean floor.

The research could provide important clues about how life began on Earth. Some bacteria feed on methane. If methane were present in the mantle, it could support populations of microbes, allowing them to survive in such an extreme environment. It may also be worth looking for underground stores of methane on Mars and other planets when searching for signs of life.—E. Sohn

Going Deeper:

Goho, Alexandra. 2004. Deep squeeze: Experiments point to methane in Earth’s mantle. Science News 166(Sept. 25):198. Available at http://www.sciencenews.org/articles/20040925/fob7.asp .

Information about the origin of fossil fuels can be found at www.all-science-fair-projects.com/
science_fair_projects_encyclopedia/Fossil_fuel (Science Fair Projects Encyclopedia).

But, once you feel the floor start to sway or you look out the windows only to see a vast expanse of blue, you know this is no typical science lab. Instead, the seven floors of research space are a “floating university” on board a ship called the JOIDES Resolution.

The JOIDES Resolution drillship is 469 feet long and 69 feet wide. The ship’s derrick towers 202 feet above the waterline.

Integrated Ocean Drilling Program

Last June, the 60 scientists aboard the Resolution set sail for the waters off British Columbia. They drilled holes deep into the ocean floor and conducted experiments that they hope will provide clues about what’s happening in these largely unexplored areas.

“We know more about Mars and the moon than we do about the ocean and its evolution,” says Steve Bohlen. He’s president of the Joint Oceanographic Institutes, the organization that manages the expedition.

This month, the ship is in waters off Costa Rica, drilling more holes deep into the seafloor. It will later head for the North Atlantic, looking for evidence of climate change in the distant past.

Deep knowledge

To study the layers of mud, silt, and rock that lie beneath the sea, scientists take core samples. They gather these long tubes of material by drilling a narrow, vertical hole into the crust. The researchers then analyze the material, layer by layer.

The drilling derrick looms above the research ship.

Kate Ramsayer

A tube’s different layers of rocks and sand and tiny fossils of ancient organisms provide a timeline of what happened on Earth in a given location over the last 200 million years or so.

The first ocean drilling program in 1968 gave scientists evidence that Earth’s crust was divided into huge plates. These plates slowly move around, spreading apart, slipping under, or rubbing past each other.

Since then, researchers have used cores from around the world to track changes in climate or understand why some areas are rattled by earthquakes. One core drilled near Florida contained greenish glassy particles. Geologists say the particles are evidence that a hefty meteorite slammed into the Gulf of Mexico 65 million years ago.

The new drilling program aims to delve even deeper into the mysteries of the ocean.

It’s the biggest earth science program we have, says Andrew Fisher. He likens it to the Hubble space telescope, which astronomers have used to probe outer space and make discoveries about the universe. Fisher is a professor at the University of California, Santa Cruz, and was one of the leaders of the Resolution‘s June expedition.

Resolution research

Research continues nonstop aboard the Resolution. The crew and scientists work in rotating, 12-hour shifts, with no days off, for all the days the ship is at sea. Expeditions can last as long as 55 days.

Researchers examine core samples obtained by drilling into the seafloor.

Ocean Drilling Program

To gather data, an experienced crew lowers drill pipe through thousands of feet of water in order to grind through 2,000 feet of mud and rock. Sometimes, they have to locate a hole bored into the seafloor years before so that researchers can obtain a fresh sample.

Getting the drill pipe into such a hole is like standing on top of the Empire State Building and trying to get a straw into a Coke bottle on the ground, says staff scientist Adam Klaus of Texas A&M University in College Station.

To provide a steady platform, the ship has special engines to keep it in place, even in choppy seas.

When technicians remove a sample from the drill pipe, the call of “core on deck” brings the scientists running. They immediately label the core sample and split it down the middle. One half is carefully wrapped up and archived so that scientists can study it later.

The other half is subjected to all kinds of tests, right on the boat.

Researcher Adam Klaus touches an instrument used to measure the density and composition of sediment cores.

Kate Ramsayer

Microbiologists quickly isolate samples in a sterile environment so that rock-dwelling bacteria won’t suffer contamination. Geologists describe the sediment layers and take measurements of their volumes, densities, and magnetic properties. Scientists box up samples to take to their home laboratories.

Earth’s plumbing system

In the holes left by the drill pipes, researchers stash sensors that detect and record temperature, pressure, and water seepage in the rock surrounding the hole. These sensors will gather data for a few years before the scientists send robot subs to collect the information.

Fisher and his colleagues plan to establish a network of sensors in the ocean floor to study water flow in Earth’s crust. Eventually, they hope to be able to pump water into one hole to see if it comes out in another hole. Such experiments will tell them more about how the “plumbing system” within Earth’s rocks works.

Other investigators are excited about the tiny microbes that can live in rocks more than 2,000 feet below the surface.

Oregon State University graduate student Mark Nielsen is interested in how the microbes store and handle energy deep within the rock. These microbes can’t use photosynthesis—there’s no sunlight—or many of the other processes used by bacteria. Neilson’s samples may tell him which chemical compounds the organisms take up.

Such studies could be useful in the search for life on other planets. Some scientists have suggested that, if life exists on Jupiter’s moon Europa or Saturn’s moon Titan, it could resemble the microbes that dwell in the equally hostile environment of Earth’s crust.

Life on a boat

Working on a research ship isn’t always easy. The scientists are away from family and friends for almost 2 months. Although they have access to e-mail, all 110 people on board the ship must share one telephone for personal calls.

Plus, with 12-hour working days and labs that don’t always have windows, a researcher’s sense of time can get out of whack.

“You can’t tell the day, and time doesn’t matter,” says Verena Heuer. She’s a microbiologist from Bremen University in Germany. “It’s just the sea and you and the ship,” she says.

Scientists and staff aboard the research ship share rooms with one or three other people.

Kate Ramsayer

Two days before the ship’s departure, Heuer and some friends took long walks. Once they were aboard, their strolling options were strictly limited.

Packing for the trip often included special personal items. Klaus brought pictures of his family. Nielsen stocked up on chocolate, Sour Patch Kids, and books. He also bought an iPod music player specifically for the trip. Heuer packed coffee and said that as long as she didn’t run out of chocolate, she’d be a happy camper.

For the scientists, the chance to be with other scientists to share ideas, ask questions, and conduct experiments makes up for the tough living conditions.

“I’m always humbled when I come to a port and see a ship waiting and know I get to go out on it,” Fisher says. “There are people from all different countries doing all different kinds of research. There’s nothing like it in the world.”

Going Deeper:

News Detective: Kate Visits a Research Ship

Word Find: Deep-Sea Drilling

Additional Information

Questions about the Article

JOIDES Resolution Facts

From January 1985 to September 2003, the JOIDES Resolution operated for 6,591 days, traveling a total distance of 355,781 nautical miles, visiting 669 sites to drill 1,797 holes and recover 35,772 cores. Its deepest hole penetrated 6,926 feet (1.31 miles) into the ocean floor.

The ship itself is 469 feet long and 69 feet wide. Its derrick rises 202 feet above the waterline. The crew positions the ship over a drill site using 12 computer-controlled thrusters as well as the main propulsion system. The rig can suspend as much as 30,020 feet of drill pipe to an ocean depth as great as 27,018 feet.

Source: www-odp.tamu.edu/shipstats.html and www-odp.tamu.edu/shiphist.html (Ocean Drilling Program, Texas A&M University)