Camilla Jessen
Scientists rethink origins of complex life.
For decades, experts have tried to explain how simple cells evolved into the complex organisms that make up plants, animals and fungi.
While Charles Darwin’s theory of evolution describes how species change over time, the deeper origins of complex cells have remained harder to pin down.
Now, researchers at the University of Texas at Austin believe they have uncovered important insights into the ancient microbes that may have paved the way for complex life.
Their findings focus on mitochondria, the structures inside cells responsible for producing energy and often referred to as the powerhouse of the cell.
Oxygen and evolution
Living organisms are broadly divided into two main cell types. Eukaryotes contain internal compartments such as a nucleus and mitochondria, while prokaryotes, including bacteria and archaea, lack these structures.
Complex life forms are made up of eukaryotic cells.
Scientists have long thought these cells emerged when an ancient archaeal cell, known as an Asgard archaeon, absorbed a bacterium that later evolved into mitochondria.
Earlier research suggested that these archaea thrived in environments with little or no oxygen. However, the University of Texas team reports evidence that some Asgard archaea can tolerate or even use oxygen.
Speaking to IFLScience, study lead Brett Baker said: “One of the big questions in biology and evolution of life on the planet is what events led to the formation of complex life (plants and animals). This study provides new clues about the lifestyle of our microbial ancestors, and we think they could breathe oxygen like us!”
Genetic expansion
The researchers examined genetic material from shallow coastal sediments, where they observed microbial interactions similar to those believed to have triggered the emergence of eukaryotic cells.
According to the team, their sequencing work significantly expanded the number of known genomes linked to these archaea.
Author Kathryn Appler said: “This massive sequencing effort nearly doubled the number of genomes from the closest known archaeal relatives of the host that gave rise to eukaryotes, providing a more comprehensive view of their ecology and metabolism.”
Baker added: “Most Asgards alive today have been found in environments without oxygen. But it turns out that the ones most closely related to eukaryotes live in places with oxygen, such as shallow coastal sediments and floating in the water column, and they have a lot of metabolic pathways that use oxygen. That suggests that our eukaryotic ancestor likely had these processes, too.”
Sources: IFLScience, University of Texas at Austin
