Biologist busts the myth of the ‘unicorn’ bacteria

"This outlying result was always there, always lingering in published papers," says Maren Friesen. "Now we've been able to bury this once and for all." (Credit: sharyn morrow/Flickr)

Plant biologist Maren Friesen has been on a quest to find near-mythical bacteria that could fix their own nitrogen. Her search was based on results from Germany published in the 1990s that seemed to confirm their existence.

The end result, published in the current issue of Scientific Reports, proves the elusive bacteria, Streptomyces thermoautotrophicus, do in fact exist but don’t have any mythical qualities.

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 appeared to have exceptional properties, including harboring a special enzyme that was insensitive to oxygen.

Why go on such a quest?

Some unicorns are worth chasing, says Friesen.

“If they actually existed, 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,” says Friesen. “In this dream world, 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.”

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While Friesen and an international team of scientists remained highly skeptical of the bacteria’s existence, the positive result in the literature had long tantalized researchers. However, there were no other papers from independent labs to confirm the original findings.

“This outlying result was always there, always lingering in published papers,” Friesen says. “Now we’ve been able to bury this once and for all.”

How the myth got its start

The myth 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. She was somewhat surprised that she was able to find the bacteria, lending a bit of credence to the myth.

The tale grew even more when they 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 says. “For the next experiments, we had to introduce a number of new controls, which included washing or purifying the gas we used.”

“Reproducibility is really key to good science.”

Dispelling the myth turned out to be a roller coaster of results and reactions—from actually finding the missing bacteria to a positive result that bolstered the tall tale, and from conducting many, many more experiments to finally killing the bacterial “unicorn.”

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 says. “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 researcher’s data than believe a singular result. Reproducibility is really key to good science.”

The National Science Foundation funded part of the research.

Source: Michigan State University