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Hemimastigotes were assigned to an entirely new branch of the evolutionary tree of life. The microbes living in the earth are so unusual that they do not fit into any known body kingdoms. As a result, the microbes have been placed in their own new branch, which is an extremely rare event.
Hemimastigotes were first observed in the 19th century, but they have never been well studied. The new research, which aimed to explore the identity of hemimastigotes, revealed that these microbes are very different from other eukaryotes – life forms that have complex cells and a clearly defined nucleus.
Hemimastigotes measure about two hundredths of a millimeter and move using more than a dozen hairs called flagellae. They are so different from everything that has been observed before that fungi and animals are actually more closely related.
"They represent a major branch … that we did not know we were missing," said Alastair Simpson, lead author of the study and professor of biology at Dalhousie. "We do not know anything closely related to them."
The researchers reported that the discovery was made by a member of the team who was investigating the microbial species present in the earth. When she examined a soil sample taken during a hike, she discovered unusual microbes. These were in fact two species of rarely observed hemimastigotes, which had not yet been attributed to an evolutionary family tree. Later, the researchers were able to analyze hundreds of other samples, which made it possible to understand very clearly the genetic composition of the microbes.
When a new microbial species is identified and its genetic information is compared to other species, it has been placed only in existing kingdoms. But the researchers had to create an entirely new branch on the evolutionary tree of life to place the hemimastigotes.
"This discovery literally redefines our branch of" The Tree of Life "at one of its deepest points," said Dr. Simpson.
"Our analyzes clearly showed that hemimastigotes did not belong to any known group at the kingdom level, nor even to a known" supergroup "of several united kingdoms, such as the one that includes both animals and fungi. This small collection of organizations is a whole new group at this level, alone. It's a branch of the tree of life that has been separated for a very long time, perhaps over a billion years, and we had no information about it. "
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