Can Deep-Sea Microbes End the Search For the Origin of Complex Life?


Hot Springs in Yellowstone Housed the New Species

Let us introduce Thor, Loki, Odin and Heimdall – our microbial ancestors dating back two billion years. A team at Uppsala University, Sweden has discovered several microbes carrying genes that were previously thought to be unique to more complex life forms, including humans.

The single-celled microorganisms, called archaea, were discovered in aquatic sediments collected at seven sites around the world, including hydrothermal vents in the Arctic Ocean and hot springs in Yellowstone National Park. The four species in question, named after Norse gods and known as ‘Asgard archaea’, are as different from one another as a tree is from a mushroom.

The finding supports a decades-old theory that complex life first arose when an archaeon consumed a bacterium, but the bacterium survived. The resulting arrangement proved to be beneficial to both, and the two previously separate organisms evolved into life forms with cells and complex internal structures, called eukaryotes. All plants and animals are eukaryotes.

“The things which we thought made a eukaryote a eukaryote, [are what] we’re now finding in these new archaea,” said researcher Brett Baker. “We’re essentially rewriting the textbook on basic biology.”

So far, the archaea have only been identified by piecing their genomes together using separate bits of gathered genetic material. The team’s next goal is to grow them in the lab.

“It would be great if we could isolate or grow Asgard cells, and study them under the microscope,” said Thijs Ettema, a researcher who was involved in the project. “I am convinced that this will reveal more important clues about how complex cells evolved. Ultimately, our microbial ancestry will be uncovered.”