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Mysterious Bacteria Cannot Fix Its Own Nitrogen After All

Maren Friesen

Maren Friesen, Michigan State University plant biologist, has found that an elusive bacteria, known as Streptomyces thermoautotrophicus, does not in fact have the exceptional properties that some scientists had hoped.

According to Friesen, most nitrogen-fixing bacteria use an enzyme that does not work when oxygen is present. The heat and toxic gas-loving strain that Friesen studied, however, originally appeared to harbor a special enzyme that was insensitive to oxygen.

“If the bacteria actually had those properties, it would mean we could have plants that could fix their own nitrogen, a compound used in critical biological functions, with no need for nitrogen fertilizers,” said Friesen. “If so, there would be less pollution, less nitrogen runoff into rivers and streams, less greenhouse gas emissions, less fuel being used to transport and apply fertilizer.”

The myth about Streptomyces thermoautotrophicus began in Germany, where the bacteria were discovered. They thrived in the hot, toxic fumes over traditional charcoal fires where large quantities of wood were buried and burnt down.

Friesen’s collaborators traveled to Germany and gathered samples while she went to Centralia, Pa., where underground coal fires have been burning for decades.

Initially the scientists produced a positive result in the laboratory, demonstrating that the bacteria did indeed fix their own nitrogen. This, however, turned out to be a tainted result.

“We learned that the gas that everyone had been using for the experiments was contaminated,” Friesen said. “For the next experiments, we had to introduce a number of new controls, which included washing or purifying the gas we used.”

In addition to setting the record straight on the bacteria’s properties, the study also had a positive impact on the concept of international collaboration and open data. Scientists from Harvard University, Imperial College (London), Aachen University (Germany) and Universidad Nacional de Rosario, Zavalla (Argentina) contributed to key aspects of the research. Rather than focus on one experiment, the team conducted many experiments around the world.

“By sharing data, you can have a lot of influence,” Friesen said. “The most-influential datasets are the ones that everyone is using. And as this research demonstrated, it’s better to compare your results to other researchers’ data than believe a singular result. Reproducibility is really key to good science.”

Friesen’s research was funded in part by the NSF.

– excerpted from Layne Cameron, Maren Friesen via MSU Today

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