A stromatolite field in Shark Bay, Australia
On the shores of Australia’s west coast, a window into our past has been discovered: the stromatolites and microbial mats of Gathaagudu.
To ‘non-experts’ they look like just a collection of rocks and silt – but in fact they are teeming with microbial life.
Os stromatolites Featured in the image are living “relics” of ancient ecosystems that thrived on Earth billions of years ago.
The first bubbles of oxygen that filled the early Earth’s atmosphere likely came from ancient stromatolites. It can be said that We owe our very existence to these piles of rocks.
So, what other secrets from our past could these ecosystems reveal? Through decades of research, we know how primitive life made its way through these “living rocks.” However, recently scientists began the greatest genealogical quest of all: looking for our great microbial ancestors, the archaea Asgard.
In a new study, this Thursday in Current Biologyit is shown how this search led to the discovery of a fundamental clue that could help explain how complex life evolved on Earth.
The cells that make up complex life
The Asgard archaea were originally named after the Norse gods. This fascinating group of microbes is on the threshold of one of the most significant events in the evolution of life: the origin of the complex cells that make up plants and animals, known as eukaryotes.
Evidence suggests that the Asgard archaea are the closest relatives of eukaryotes. And that, on a primitive Earth, it was the “marriage” of an ancestral Asgard archaea with a bacterium that gave rise to the first eukaryotes.
They formed an old partnership. They shared resources and interacted physically, leading to the first complex cells. However, until the new study we had never seen a model of how this could have occurred.
Mirror of the past
The team used the Shark Bay rugs like a “seed” to establish cultures of these ancient microbes.
But the Asgards were not alone. They were found together with a sulfate-loving bacteria. Could this be a model for how complex life may have begun on an early Earth?
As he explains in an article on , the team believes these two microbes were sharing nutrients. In other words, they were cooperating.
However, the researchers wanted to delve deeper.
After all, what are our great microbial ancestors like? To find out, electron cryo-tomography was used, a high-resolution imaging approach that allowed cells and structures to be observed on a nanometric scale.
For the first time, a archaea Asgard and a bacteria interacting directly. Tiny nanotubes were connecting the two organisms – perhaps reflecting what their great ancestors did on an early Earth that will eventually lead to the explosion of complex life as we know it.
