Australian scientists discover a tiny microbe that could shed light on the origins of human life World News
Scientists have discovered an archaea called “Asgard” in the extremely salty waters of Australia’s Shark Bay, containing microorganisms that contribute to a long-standing mystery of evolution for many centuries – how did simple single-cell bacteria develop into such complex multi-celled organisms, animals and humans? These unique microbes serve as evolutionary nexus; they carry cellular machinery thought to be unique to complex cells, thereby showing us evolutionary transition points in evolution. Proto-eukaryotes, which we now call “living fossils,” represent specific initial microorganisms that could exist in and consume other initial microorganisms. This created the first eukaryotic cell. Without this unique microscopic ancestor found in Australia’s hypersaline basin, the branch of the evolutionary tree that represents humans would never have developed.
A microorganism discovered in Australia reveals the secrets of our existence
The identification of Asgardian archaea found in Shark Bay microbial mats suggests they are the closest living relatives of eukaryotes, or living organisms in cells, including humans, according to the study published in the journal Nature. Asgard archaea contain so-called “eukaryotic signature proteins” (ESPs), which provide molecular scaffolds for intracellular structures. DNA analysis suggests that Asgardian archaea represent a eukaryotic ancestor, establishing a direct evolutionary lineage between this single-celled organism and modern humans.
How endosymbiosis fueled the rise of multicellular life
Research related to Asgardian archaea supports the endosymbiosis theory. According to the theory, published in the Proceedings of the National Academy of Sciences, endosymbiosis begins when an Asgard-like organism devours some unrelated bacteria. Rather than digesting the bacteria, the larger Asgardian cells and bacteria exist together as symbionts. Over millions of years, the engulfed bacteria evolved into what we now call mitochondria—the “engines” of our cells that provide the metabolic surge needed to evolve to produce multicellular organisms.
How Asgardian archaea bridge a two-billion-year gap
Shark Bay’s extraordinary microbial mats and living stromatolites are likely responsible for its World Heritage status, with twice the salt content of the open ocean, they are spectacular. The ancient environment they lived in was similar to the oceans of 2 billion years ago, allowing scientists to see a current version of the conditions that gave rise to complex life through the Asgardian archaea, which now live in this specific ecological niche and are considered the “missing link” because they exhibit evolutionary plasticity.
The hidden complexity of simple microorganisms
Additionally, Asgardian archaea have a unique cytoskeleton compared to standard prokaryotic cells; this allows the cells to change their shape and move, and potentially transport materials internally, which was once thought to be associated only with complex life forms, reports the Journal of Molecular Biology. Thus, they provide evidence that the cellular biomechanics necessary for complex, environment-dependent life forms existed before the first animals emerged.
