Suspected anthrax mailer Bruce Ivins was a prolific contributor to research articles in the arcane field of deadly pathogens, and was named as a co-author in more than 40 studies published in scientific journals since the late 1960s.

But in the last 10 years or so, Ivins' role seemed to have shifted to that of a supporting player, albeit a highly skilled one. During the 1990s, Ivins was credited as the lead author on four out of 12 published journal articles. After 2000, he contributed to 16 articles, but was not named as the first author on any. His greatest prominence as a scientific author came during the 1980s, when he was the lead writer on seven articles.

Ivins, a government scientist who committed suicide last week, has been identified by officials as the suspect in the 2001 anthrax attacks that killed five people and infected 17 others.

John W. Ezzell, the former top anthrax specialist at the Army biodefense facility where Ivins worked, said his one-time colleague was cited so frequently in recent years because he provided the anthrax spores that were used in a range of experiments with animals.

"He got his name on a lot of these publications because he was providing the spores," said Ezzell, who retired from the U.S. Army Medical Research Institute of Infectious Diseases at Fort Detrick, Md. "That is one of the reasons he was on so many publications. So many of the studies were conducted with his spores."

The articles themselves are the product of scientific teamwork, written in terse, technical language that average readers would find difficult to parse. They reflect the stuff of basic science: trial-and-error investigation. While the writings do not appear to provide any obvious clues in the anthrax investigation, they do attest to the breadth of Ivins' involvement in anthrax research.

Another former colleague, Jeff Adamovicz, said the articles only provide a partial portrait of Ivins' scientific work. Ivins' detailed knowledge of the anthrax bacteria proved valuable in developing a new vaccine prototype and in devising tests to see if it would work on animals, Adamovicz said.

Ivins is the first scientist listed on a patent for a new anthrax vaccine that was developed by a Fort Detrick team. It has been licensed for development and may one day be used by first responders in a bioterror attack. The patent was filed for in 2000 — before the anthrax mailings — and was granted in 2002.

"He worked best as a member of a team," said Adamovicz, who specializes in plague, and is now a consultant. "He was not a lone-wolf kind of guy. He liked to work with other people and solve technical problems."

The kind of spores that Ivins produced for experiments was not in the form used in the anthrax mailings. According to Adamovicz, Ivins worked with "wet" spores, which are kept in a watery solution. The spores used in the attacks were "dry" spores, which have been processed several more steps to allow for their release into the air.

Ivins was "really critical in identifying better methods of spore production, and in refining the (qualities) of these spore lots so they had consistent characteristics in terms of concentration and viability," Adamovicz said.

Ezzell said some of Ivins' most important research came in the early 1980s, when he assisted another scientist, Joseph D. Ristroph, in developing a new medium for growing anthrax antigens. An antigen is a substance that triggers an immune system response, and is key to developing a vaccine. The new method could produce levels of antigens that were five times greater than previously possible.

Some two decades later, Ivins helped develop the science behind the new vaccine at Fort Detrick. The vaccine works by stimulating the immune system.

Anthrax bacteria make three different proteins to poison cells in living tissue. One of them, called "protective antigen," starts the process. It opens blood cells to let its more toxic cousins inside.

The Detrick team created a genetically modified version — a skillful fake — called the recombinant protective antigen, or rPA. It stimulates the immune system so that the body will recognize and fight real anthrax later if a true infection occurs.