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Scientists Discover New Branch Near Roots Of Tree Of Life

Published: Thursday, December 27, 2018 - 4:27pm
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Yana Eglit, Patricia Scallion, DalTech SEM facility.
A scanning electron microscope reveals the hemimastogote, a complex single-celled organism from near the roots of the tree of life.

The search for the roots and earliest branches of the tree of life can take scientists into unusual territory — including an ancient offshoot that's in a class by itself.

"We have effectively discovered a new fundamental group of living eukaryotic cells. The information from that group is very important to working out how complex cells evolved in the past," said co-author Alastair Simpson of the Centre for Comparative Genomics and Evolutionary Bioinformatics at Dalhousie University in Halifax, Nova Scotia, Canada.

The research appears in the journal "Nature."

Human beings share more in common genetically with fungi than they do with hemimastigotes, the new group of eukaryotes, or complex single-celled organisms, described by researchers in Nova Scotia.

Scientists have known about the microscopic predators, which sport two sets of hairlike flagella and an unusual cell structure, since the 19th century. But only after recent technology enabled researchers to genetically analyze them using only a few cells did experts fully realize the creatures' distinctiveness.

"The way we did the work would not have been possible maybe more than five years ago because the techniques weren't available," said Simpson.

Scientists have placed nearly all eukaryotes into five to eight groups. On the great tree of evolutionary history and classification, these lie above the kingdom level, where plants, animals, fungi and bacteria split, but below the domain level, where eukaryotes all group together.

"If you were to divide eukaryotes — so, complex celled organisms — into the half-dozen most fundamental branches then, at that level, animals and fungi are both together in one of those branches," said Simpson.

Previous attempts to place hemimastigotes in the tree relied solely on morphology. This new research lets scientists spot genetic similarities and differences that are more than skin-deep.

The researchers also discovered a new species, Hemimastix kukwesjijk, within the new supra-kingdom. In the traditions of the Mi'kmaq First Nation of Nova Scotia, Kukwes is the name of a hairy, insatiable ogre.