Scientists Describe New Form of Life as ‘Weird Bug’

Scientists have discovered an entirely new type of creature--one that does not fit into any previous category of life--lurking in an undersea vent north of Iceland.

The creatures are small spheres attached to other organisms and are so genetically strange and so tiny--smaller than a grain of sand and about the width of four human hairs--that they were invisible to traditional ecological survey methods.

“Even the ultimate molecular ecology methods could not detect our new microbes because they are so different from everything known so far,” said Karl Stetter, a professor of microbiology at the University of Regensburg in Germany who led the discovery team.

Stetter and his colleagues detected the creatures only after growing them in hot, oxygen-free and high-pressure conditions to simulate their natural hostile environs.

Sharp eyes and a nifty lab tool called optical tweezers--which let scientists manipulate tiny and fragile objects with a laser beam focused through a microscope--allowed Stetter’s team to separate the organisms from their hosts. But they could not survive separately, suggesting they are symbionts.

Molecular ecologists use existing DNA probes to hunt for new organisms. Because this creature is such a “weird bug,” said evolutionary biologist W. Ford Doolittle of Dalhousie University in Nova Scotia, the German scientists needed to create customized genetic tools to detect it.

The DNA of the “nano-sized hyperthermophilic archaeon” is interesting because it is so minimal. Containing just 500 kilobases, the genome is among the smallest known. (Compare it to 6 million kilobases for humans and 9 million for corn.)

The genome is smaller than some viruses and in the range of the smallest living organisms known--mycoplasma, or bacterial parasites.

In an article accompanying the new research in the current issue of the journal Nature, Doolittle called it “a genome begging to be sequenced.” Stetter, who is also a faculty member at UCLA, said it provides “insights into the minimum equipment of a living cell.”

The new creatures, formally named Nanoarchaeum equitans, may represent an entirely new grouping with the Archaea, the most mysterious of life’s three domains. (The others are eukaryotes--organisms with nucleated cells like people, plants and fungi--and bacteria.)

And even stranger discoveries could lie ahead. “There is a very good chance,” Stetter said, “that still-undiscovered continents of microbial life do exist on our planet.”