Biology

New branch on Tree of Life contains organisms unlike any others on Earth

A microscope image of a Provoran, a micro-organism from the newly discovered supergroup
Tikhonenkov, Mikhailov, Gawryluk, Belyaev, Mathur, Karpov, Zagumyonnyi, Borodina, Prokina, Mylnikov, Aleoshin, and Keeling, Nature
A microscope image of a Provoran, a micro-organism from the newly discovered supergroup
Tikhonenkov, Mikhailov, Gawryluk, Belyaev, Mathur, Karpov, Zagumyonnyi, Borodina, Prokina, Mylnikov, Aleoshin, and Keeling, Nature

Scientists have discovered a completely new branch on the tree of life. This “supergroup” contains an incredibly diverse range of predatory microbes that are extremely different genetically from any other form of life on Earth.

The tree of life is a useful diagram for understanding the relationships between different forms of life, present and extinct. The trunks are made up of three broad groups called domains – Bacteria, Archaea and Eukaryota – which then branch into kingdoms such as animals and fungi. From there the branches become more and more specific until you reach individual species.

The new discovery adds quite a major bough to the tree – Provora. These lifeforms make up a category informally called a “supergroup,” which sits below domains and can contain multiple kingdoms.

“This is an ancient branch of the tree of life that is roughly as diverse as the animal and fungi kingdoms combined, and no one knew it was there,” said Dr. Patrick Keeling, senior author of the study.

Members of the Provora supergroup are tiny organisms that the team describes as the “lions of the microbial world.” That’s because they prey upon other microbes, and within their ecosystem they’re relatively rare. The supergroup is further divided into two clades – the “nibblerids,” which use tooth-like structures to nibble chunks off their prey, and the “nebulids,” which engulf their prey whole.

The team discovered this new kind of life in samples taken from around the world, including the coral reefs in Curaçao, sediment from the Black and Red seas and water from the Pacific and Arctic oceans. The researchers’ attention was drawn to strange microbes with two flagella, allowing them to spin or swim very quickly. They also had a tendency to quickly gobble up any other microbes unfortunate enough to be kept in the same water samples. When the scientists examined their DNA more closely, it became clear just how weird these new microbes really were.

“In the taxonomy of living organisms, we often use the gene ‘18S rRNA’ to describe genetic difference,” said Dr. Denis Tikhonenkov, first author of the study. “For example, humans differ from guinea pigs in this gene by only six nucleotides. We were surprised to find that these predatory microbes differ by 170 to 180 nucleotides in the 18S rRNA gene from every other living thing on Earth. It became clear that we had discovered something completely new and amazing.”

Next, the team plans to sequence the whole genomes of these new organisms and build 3D models of their cells, to learn more about them.

The research was published in the journal Nature.

Source: University of British Columbia

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6 comments
Cryptonoetic
How can something this significant go unobserved for so long? Never believe that "the science is settled"!
mattlass
This discovery reinforces my long-held belief that we know an infinitesmal amount in an infinite world of knowledge. The hubris of scientists and their dismissal of phenomena that ancient civilizations have introduced is scandalous. Congratulations to these discoverers, but they've just scratched the surface.
NigelThompson
Pictures, I want pictures. And movies of them in action. Show me the wildlife in action
Broadlands
It should be obvious that these organisms are not close to the base of the tree-of-life. As aerobes they are above the cyanobacterial lineage that provides oxygen.
TechGazer
Provora offer hope for new medicines, biochemicals, and possibly pest control and other uses. Maybe they cause some human--and plant and animal--diseases too, and knowing about them could lead to proper diagnoses and treatments.

Are there a bunch of microbiologists slapping their foreheads because they'd seen these organisms before and just dismissed them as mutants?
Zane Wright
The Povora and the "supergroup" must not to be the first group. What the "supergroups" ate the bacteria, archaea and the Eukaryota?