Canadian researchers have discovered a new kind of organism that's so different from other living things that it doesn't fit into the plant kingdom, the animal kingdom, or any other kingdom used to classify known organisms.

Two species of the microscopic organisms, called hemimastigotes, were found in dirt collected on a whim during a hike in Nova Scotia by Dalhousie University graduate student Yana Eglit.

A genetic analysis shows they're more different from other organisms than animals and fungi (which are in different kingdoms) are from each other, representing a completely new part of the tree of life, Eglit and her colleagues report this week in the journal Nature.

"They represent a major branch… that we didn't know we were missing," said Dalhousie biology professor Alastair Simpson, Eglit's supervisor and co-author of the new study.

"There's nothing we know that's closely related to them."

In fact, he estimates you'd have to go back a billion years — about 500 million years before the first animals arose — before you could find a common ancestor of hemimastigotes and any other known living things.

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The hemimastigotes analyzed by the Dalhousie team were found by Eglit during a spring hike with some other students along the Bluff Wilderness Trail outside Halifax a couple of years ago. She often has empty sample vials in her pockets or bags, and scooped a few tablespoons of dirt into one of them from the side of the trail.

Back at the lab, she soaked the soil in water, which often revives microbes that have gone dormant, waiting for the next big rainstorm. Over the next few weeks, she checked on the dish through a microscope to see what might be swimming around.

Strange movements

Then, one day, about three weeks later, she saw something that caught her eye — something shaped like the partially opened shell of a pistachio. It had lots of hairs, called flagella, sticking out. Most known microbes with lots of flagella move them in co-ordinated waves, but not this one, which waved them in a more random fashion.

"It's as if these cells never really learned that they have many flagella," Eglit said with a laugh. She had seen something with that strange motion once before, a few years ago, and recognized it as a rare hemimastigote.

Hemimastigotes were first seen and described in the 19th century. But at that time, no one could figure out how they fit into the evolutionary tree of life. Consequently, they've been "a tantalizing mystery" to microbiologists for quite a long time, Eglit said.

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