‘Impossible’ Single-Cell Organism Discovered

A team of researchers from the University of Jena has discovered prokaryotic bacteria that can eat other cellsan amazing find published in the magazine mBio.

He origin of eukaryotes It is considered one of the greatest mysteries of biology: according to the current theory, two prokaryotes, the so-called Asgardian archaea, and a bacterium are thought to have merged. The bacteria evolved into mitochondria. This gave this eukaryotic ancestor enough energy to develop into the most complex cells we know today.

The defining characteristic of these complex eukaryotes is endocytosisthat is, the ability to devour other cells. However, until this new study, it was considered energetically impossible for a prokaryotic cell to be capable of endocytosis, since the mitochondrial energy source was considered necessary for this.

Professor for over 10 years Christian Jogler and his team were looking for a different approach to explaining eukaryogenesis. The researchers focused on a group of prokaryotes. planctomycetesvery unusual bacteria that some scientists believe may be the ancestors of eukaryotes because of their unique cell biology.

“The idea of ​​‘merging’ two different prokaryotes into a eukaryote seems to me to be incomprehensible from a cell biology perspective,” explains the microbiologist, who conducts research at the Balance of the Microverse excellence cluster, in a statement from the University of Jena. “No one has seen anything like this before, and such a hybrid would probably not be viable due to the different membrane structures and molecular mechanisms,” adds Jogler.

In 2014, Professor Jogler’s team discovered new planctomycetes in Heiligendamm, in the Baltic Sea, which provided arguments in favor of the planctomycete origin of eukaryotes. “These bacteria change shape, “walk” on surfaces and flow around each other.”

In 2019, the team under the leadership Takashi Shiratorifrom Japan also discovered and described similar planctomycetes. These microorganisms even fed on other bacteria and therefore seemed to refute the doctrine that prokaryotes are incapable of endocytosis for energetic reasons.

“To be honest, I didn’t believe Dr. Shiratori at first,” says Jogler. That’s why he and his team initially tried to disprove the prokaryotic endocytosis hypothesis. But after a year of intensive research, the researchers no longer doubted the accuracy of Shiratori’s results.

Beyond the norm

In the paper they have now published, they present a similar organism that they isolated and characterized from the North Sea: Uabimicrobium helgolandensisThese prokaryotes also feed on other bacteria and therefore They shouldn’t even exist.The researchers gave this group of unusual planctomycetes the apt name “prey bacteria.”

“Thanks to genome sequencing, Uabimicrobium helgolandensis“We were also able to develop new hypotheses about the molecular mechanism of bacterial prey uptake,” explains Jogler.

This expert believes that predatory planctomycetes are microbes Archaeopteryxa bridge organism between prokaryotes and eukaryotes, and is convinced that planctomycetes played a role in eukaryogenesisperhaps even in the origin of life itself.