Arsenic discovery has ties to Pittsburgh

Duquesne professor, former resident played key roles in research

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The announcement Thursday that a team of researchers found the first known living organism to operate on something other than the six basic elements for life began with a news conference in Washington, D.C., and reverberated around the world.

Some of those reverberations were felt directly in southwestern Pennsylvania.

Two of the 12-member team that discovered a bacterium that can use arsenic to live in place of phosphorus -- one of those six basic elements -- are from the region and played crucial roles in the research. The other five basic elements that are key to life are carbon, hydrogen, nitrogen, oxygen and sulfur.

Jennifer Pett-Ridge, a staff scientist at the Lawrence Livermore National Laboratory in Livermore, Calif., who helped analyze the DNA of the bacterium, is a 1990 graduate of North Allegheny High School.

John Stolz, a professor of biological sciences at Duquesne University better known locally for his work on Marcellus Shale natural gas issues, helped prepare and analyze the bacterium cells that led to the discovery.

They've both spent much of the last two days hearing from friends, family and colleagues congratulating them, even as they watched and read in disbelief at the international reaction.

"For us, it has been a kick because we didn't think it would generate this kind of excitement," Dr. Stolz said.

Dr. Pett-Ridge said her field rarely sees this kind of interest.

"I never see any stories about microbiology on the cover of The New York Times (as this was Friday), so this has been fun," said Dr. Pett-Ridge, whose father, Chris Pett-Ridge, is a former Post-Gazette editor.

Neither was a lead author on the research paper that has shaken up the scientific world since it appeared in the journal Science this week, but their work was critical.

Dr. Stolz, 55, has worked for the last 15 years on arsenic metabolism, an area of interest he chose to spend half of his career on for fundamental reasons: "You take something -- arsenic -- that everyone knows is poisonous but some organisms need it for life. Why is that?"

Much of his work over the last decade on arsenic has been with Ronald Oremland, a researcher at the U.S. Geological Survey in Menlo Park, Calif., where the scientist who came up with the idea for the project, Felisa Wolfe-Simon, also worked.

Her idea -- that bacterium living in ecosystems of high arsenic concentrations could be adapted to live on normally toxic arsenic instead of its non-toxic cousin, phosphate -- was well known to experts in the field like Dr. Stolz, who had read a paper in 2008 in which Dr. Wolfe-Simon proposed it.

So when Dr. Oremland called Dr. Stolz in August 2009 and asked him to come "play in the mud" of Mono Lake in California and look for bacterium that might be able to live with arsenic, he agreed -- even if he had his doubts.

After Dr. Wolfe-Simon would keep the bacterium alive and growing with arsenic in her laboratory, she would send cells chemically fixed with arsenic to Dr. Stolz to prepare and analyze.

With the help of Mark Dudash, a Duquesne University undergraduate student from Mt. Lebanon, they would imbed the cells in plastic and then look at them under an electron microscope.

What Dr. Stolz first saw then was the beginning of the proof Dr. Wolfe-Simon was looking for.

The more detailed proof the team needed would come from Dr. Pett-Ridge's laboratory, where she and her colleague, Peter Weber, use a mass spectrometer called NanoSIMS.

Their NanoSIMS is one of only 20 in the world, and it functions like a very powerful microscope, allowing researchers to look at the DNA level of a cell, but also to analyze it for its makeup.

It was because of that that Dr. Pett-Ridge got involved in the project nearly a year after Dr. Stolz traipsed out to Mono Lake with Dr. Wolfe-Simon.

She was at a conference in Newport, R.I., in June, when out of the blue "this woman I had never met before came up and grabbed me and said, 'Jennifer, I need your NanoSIMS to look at arsenic in our cells,' " Dr. Pett-Ridge recalled with a laugh. "And that started it."

The woman was Dr. Wolfe-Simon, who apparently knew Dr. Pett-Ridge from her name tag alone, but was on a mission to find her.

A few weeks later, Dr. Pett-Ridge oversaw the initial analysis of the bacterium cells, which showed what Dr. Wolfe-Simon suspected: that arsenic was present in the cell.

But that wasn't the life-theory-shattering part. What came next was.

"We already knew the organism could breathe with arsenic and it could take it up into the cell," Dr. Pett-Ridge said. "But the fact that we showed that the DNA of the bacterium used arsenic instead of phosphate -- that's the big, big deal."

Some early tests on the NanoSIMS had shown that, but this past fall, after Dr. Wolfe-Simon's paper had been accepted by the journal Science, some of the initial peer reviews of the work said they needed more proof that the DNA indeed had replaced phosphate with arsenic.

So, for two frantic weeks in October, Dr. Pett-Ridge and Dr. Weber, the lab leader, worked 10 to 12 hours a day just analyzing DNA in the bacterium to get the proof necessary.

"For two weeks it was Peter and I going back and forth," Dr. Pett-Ridge recalled.

"It was a wearing down of our own disbelief process over those two weeks," she said.

Despite what was for both Dr. Stolz and Dr. Pett-Ridge some of the most exciting work they both have ever been involved with, few people beyond their colleagues on the project knew what they were working on.

Dr. Stolz said he told just one colleague when Science accepted the paper.

And it was kept so quiet -- because of Science's embargo on information until Thursday -- that one of Dr. Stolz's bosses, David W. Seybert, dean of the Bayer School of Natural and Environmental Sciences at Duquesne, didn't even know Dr. Stolz was a listed author until a reporter pointed it out on Friday.

If the work becomes accepted by other experts, Dr. Seybert said that among the array of scientific discoveries professors at Duquesne have been involved in over the decades: "This would be right at the top."

Dr. Pett-Ridge's father had a more basic response.

Chris and Jean Pett-Ridge have two daughters, Jennifer and Julie, both of whom are research scientists, "and as parents we're always a little vague about what they're really doing in science; it can be beyond us."

But Thursday's dramatic announcement?

"That brought it all home. It was kind of neat to find out what they do for a living."


Sean D. Hamill: shamill@post-gazette.com or 412-263-2579.


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