Researchers have discovered a new branch of the Tree of Life. Two tiny predators form this new branch of "Provora". These small creatures represent two different species. One type is called a nebula, which eats the entire prey. The second type is called nibblerids: Their names are inspired by their teeth-like structures used to chew prey.
These two species look the same on the surface, but they differ in fine cell structure , genetics and behavior. The team sampled water from around the world, including the coral reefs of Curacao , sediments from Black Sea and Red Sea , and water from the Northeast Pacific and Arctic Ocean .
"I noticed that in some water samples there are tiny organisms with two flagella or tails that twitch in place or swim very quickly. So I started looking for these microorganisms ," first author Dr. Denis Tikhonenkov, senior researcher at the Institute of Inland Water Biology, Russian Academy of Sciences, said in a statement.
These predators are found in seawater and freshwater around the world, but they are rare in numbers compared to many other species. This behavior and their predatory behavior lead researchers to think that they are similar to lions—numerically rare, but still very important in terms of their habitat.
"Imagine if you're an alien and sampled in Serengeti : you'll get a lot of plants, maybe there's an gazelle , but no lions. But lions do matter, even if they're rare. These are lions in the microbial world," added co-author Patrick Killing, Ph.D., professor at the University of British Columbia .
The research team found that as long as these microorganisms appear in the sample, the rest of them will disappear quickly. They decided to raise predators, which meant that they had to provide food for their prey as well as food for their prey. This is complex in itself, and international cooperation between Canada and Russia has been even more complicated in the past few years, given the COVID pandemic and Russian invasion of Ukraine.
But by cultivating these microorganisms, the team was able to extract their genetic material and found that they were different from the vast majority of other known organisms. Compared to the dendritic supergroups, things like animal kingdoms or plant kingdoms are just twigs, and these two species belong to a completely new branch.
"In biology taxonomy , we often use the ‘18S rRNA’ gene to describe genetic differences. For example, humans differ by only six nucleotides from this gene in guinea pig . We were surprised to find that these predatory microorganisms differ from 170 to 180 nucleotides from all other organisms on Earth in the 18S rRNA gene. It is obvious that we have discovered something completely new and amazing,” said Dr. Tikhonenkov.
