UBC scientists discover entirely new branch on the tree of life — and they are likely to ‘nibble’
Scientists have recently discovered a whole new branch on the evolutionary tree of life which, they say, sheds light on the global biodiversity crisis.
The researchers, mostly from the University of British Columbia, discovered rare, single-celled predators living in marine environments around the world that are genetically distinct from any other living being on earth.
Their findings, published Wednesday in the journal Nature, placed the microbes in a new supergroup of organisms they named Provora." You can think of them as the lions of the microbial world," said Patrick Keeling, a senior author of the study and a professor researching evolutionary microbiology at UBC.
They're numerically very rare. For every lion, there's thousands of animals that aren't lions," Keeling told the Star. This was why we never detected them until now, despite their presence everywhere, he said - there were too few of them to stand out.
Despite their scarcity, Provora, like lions, could play a vital role in the food chain, Keeling said: If you disappeared all the lions, not only would we all be very sad, but the whole ecosystem would change."
Keeling and his team discovered ten unique strains of Provora in total, after scouring water samples from the coral reefs of Curacao, the Red and Black seas, the northeast Pacific and Arctic oceans and more.
Each organism falls under two categories, the paper reads: there are the nibblerids," which like to nibble" their prey to death with special tooth-like appendages; and there are the nebulids," which prefer to swallow their prey whole.
They look like tiny little cells. They're very small. And they have two of these whip-like appendages called flagella' that they use to swim around and catch their food with," Keeling said. One of them sucks up whole cells and the other type nibbles away at their food, bites off little pieces of it."
Physically, Provora resembles many other microorganisms, he continued. Instead, their most distinguishing feature lies in their DNA.
Related creatures on the tree of life have similar genetics - for example, the human 18S rRNA" gene is only six nucleotides away from its guinea pig equivalent, Keeling said. When he tested the same gene in the microbes, however, he found a staggering difference of up to 180 nucleotides.
You look at their DNA sequence and you go like, holy crap. These things are not closely related to anything we've ever seen before," Keeling said.
Their DNA was so different that the researchers placed the organisms in their own supergroup, a category just below the three main domains of life. Provora sit under the domain Eukaryota, which includes all organisms with a nucleus, but above the kingdoms, like those of the plants, animals and protists.
For reference, almost all eukaryotes belong to just six supergroups; humans fall under the Opisthokonts, which includes all animals, amoebae and fungi.
For Keeling, the study is illustrative of how little we know about the microbial world, the bedrock that supports all life directly or indirectly.
It's not like we've found something that's threatening the world here," Keeling said. But the fact that we can still go out and find these organisms and don't even know they exist, underscores to me just how bad our understanding of the biodiversity on the planet really is."
If we're not careful, Keeling said, we could knock out a critical micro-organism and throw the whole system keeping us alive out of order: Unless we actually understand how the system works and how our messing with it is screwing it up, we're really dealing with a very dangerous problem."
For example, while many would think of leafy trees as being our most important source of oxygen, scientists estimate 50 to 80 per cent of the gas actually comes from microscopic plankton in the ocean. Models have shown that, as the ocean surface warms with climate change, plankton populations are expected to drop - even still, little attention is given to microbes in the ocean.
The foundations of our entire system is microbial," Keeling said. If the microbial world were to change catastrophically in its biodiversity? Well, we would all die, and so would everything else we're familiar with."
Despite its importance, scientists view the state of microbial biodiversity with profound ignorance," reads to a 2021 paper in Frontiers in Ecology and Evolution. While we know plant and animal biodiversity as a whole is trending downwards, we have no idea" where microbes are headed.
The biodiversity of microbes and the ecology of microbial ecosystems is something that we should care about a lot more," Keeling said. If humans are going to screw up and go extinct, it's probably going to be because of (them)."
Kevin Jiang is a Toronto-based digital producer for the Star. Follow him on Twitter: @crudelykevin