In NASA’s Sterile Areas, Plenty of Robust Bacteria (original) (raw)

Oct. 9, 2007

WASHINGTON, Oct. 6 — Researchers have found a surprising diversity of hardy bacteria in a seemingly unlikely place — the so-called sterile clean rooms where NASA assembles its spacecraft and prepares them for launching.

Samples of air and surfaces in the clean rooms at three National Aeronautics and Space Administration centers revealed surprising numbers and types of robust bacteria that appear to resist normal sterilization procedures, according to a newly published study.

The findings are significant, the researchers report, because they can help reduce the chances of stowaway microbes contaminating planets and other bodies visited by the spacecraft and confounding efforts to discover new life elsewhere.

“These findings will advance the search for life on Mars and other worlds both by sparking improved cleaning and sterilization methods and by preventing false-positive results in future experiments to detect extraterrestrial life,” said the leader of the study, Dr. Kasthuri Venkateswaran, a microbiologist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif.

Identifying and cataloging what microbes might survive sterilization is important in interpreting results of sampling missions to other planets, scientists said. If similar microbes turn up in alien samples, researchers could disregard the results as contamination and not evidence of extraterrestrial life.

NASA tries to protect its spacecraft and their delicate components from dust and bacteria by assembling and testing them in rooms that are meticulously cleaned of dust and dirt by having their air continuously filtered to reduce fine particles. People working in these rooms wear coveralls with gloves and sometimes wear face masks.

Researchers from Dr. Venkateswaran’s Biotechnology and Planetary Protection Group and the Lawrence Berkeley National Laboratory published the results of their tests in the European journal FEMS Microbiology Ecology.

Samples taken from clean rooms at the Jet Propulsion Laboratory, the Kennedy Space Flight Center in Florida and the Johnson Space Center in Houston revealed almost 100 types of bacteria, about 45 percent of which were previously unknown to science, the study said. While some were common types that thrive on human skin, such as Staphylococcus species, others were oligotrophs, rarer microorganisms that have adapted to grow under extreme conditions by absorbing trace nutrients from the air or from unlikely surfaces like paint.

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Hardy Microbes A researcher taking samples in a clean room, where spacecraft are built. Samples have revealed some bacteria that are new to science.Credit...Jet Propulsion Laboratory, California Institute of Technology

Traditionally, NASA has examined clean-room bacteria by taking samples of air and surfaces and trying to culture bacteria present in the laboratory. Dr. Venkateswaran said only a small fraction of bacteria could be found this way because most grow only in their native environments.

For their tests, the researchers used a genetic testing method not employed in clean rooms before, known as ribosomal RNA gene sequence analysis, which allowed them to study and decode a genetic marker common to all bacteria. The unique sequences of each type allowed the researchers to identify a greater number and diversity of bacteria than previously detected in the rooms.

While a few microorganisms, like those common on human skin, were found at all three sites, the study discovered that each room had a bacterial community largely unique to itself. Many factors could be responsible for this diversity, the researchers said, including the differing types of air filters and cleaning agents used and the facilities’ different geographic locations.

“I was surprised by what we found,” Dr. Venkateswaran said in an interview, “and as we continue to sample additional clean rooms, we may be in for even more surprises.”

Dr. Catharine A. Conley, a biologist who is the acting planetary protection officer at NASA headquarters, said the agency had long suspected that the organisms previously detected in clean rooms did not represent the full range that were there. Current cleaning techniques kill most common microbes, she said, and the resulting lack of competition could contribute to the number and diversity of the durable survivors found by the genetic testing approach.

“We know clean rooms can be much cleaner, and some are,” Dr. Conley said, citing some used by the semiconductor and pharmaceutical industries. “The problem is the cost. They are very expensive to build and maintain.”

Spacecraft going to areas where alien life is more likely to be found, like planets or moons with identifiable water, can be sterilized by a heat method that essentially bakes them for hours. But, she said, this runs the risk of damaging components.

Dr. Conley said NASA was experimenting with different techniques, including infusing spacecraft with vaporized hydrogen peroxide or a cold plasma of ionized gas, to attack the problem.

Spacecraft contamination is not just an issue for the United States, Dr. Conley noted. All space agencies sending out interplanetary probes follow cleanliness rules from an international organization called the Committee on Space Research. These standards vary depending on the type of mission, such as one that lands on a body versus orbiting it, and the likelihood that the destination bears life.

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