Chuck Bednar for redOrbit.com – @BednarChuck
Researchers from the University of Vienna have reportedly discovered “a missing link” in the evolution of eukaryotes, organisms whose cells contain a nucleus and other organelles enclosed within a membrane, from simpler single-celled known as prokaryotes.
Writing in Wednesday’s edition of the journal Nature, Dr. Christa Schleper of the Department of Ecogenomics and Systems Biology and her colleagues report on the discovery of a new, complex type of microorganism that could be the closest relatives of complex biological life.
Identified by the study authors as a novel candidate archael phylum known as Lokiarchaeota, this new microorganism “forms a monophyletic group with eukaryotes in phylogenomic analyses and whose genomes encode an expanded repertoire of eukaryotic signature proteins,” suggesting that this phylum had “sophisticated membrane remodeling capabilities.”
The Lokiarchaea form a group of Archaea, which have surprisingly similar to the ancestors of modern eukaryotes. (Credit: Copyright Christa Schleper)
They added that their findings “provide strong support for hypotheses in which the eukaryotic host evolved from a bona fide archaeon, and demonstrate that many components that underpin eukaryote-specific features were already present in that ancestor.” This served as a “genomic “starter-kit” of sorts that supported “the increase in the cellular and genomic complexity that is characteristic of eukaryotes” that was characteristic of Lokiarchaeota.
Finding proteins for membrane remodeling, cytoskeleton formation
As Dr. Schleper and her colleagues explained in a statement, genomic research has found the organelles that deliver energy in eukaryotic cells (mitochondria) stem from an early bacterial symbiont, and that current models indicate that archaea also played a key role in the evolution of eukaryotes.
Based on this information, the authors proposed that a primordial Archaeon may have engulfed a bacterium, transforming into a complex eukaryotic cell. In phylogenetic trees, Lokiarchaeota are a direct sister group to eukaryotes, they said, meaning that the ancestors of eukaryotes emerged directly from archaea, and the genome of Lokiarchaeota also revealed that it housed genetic data for some proteins that had previously only been found in eukaryotes.
Some of those proteins are responsible for membrane remodeling and cytoskeleton formation, which helps determine a eukaryotic cell’s shape, the research team said. Those featured would be required by a primordial cell or archaeon to engulf bacteria during the initial stages of eukaryotic evolution, explained first author and former Ph.D. student Anja Spang.
“It is as if we had just discovered the primates i.e. the next living relatives of humans, who also give us interesting insights into the nature of the last common ancestor,” added Dr. Schleper. “However, the common ancestor of Lokiarchaeota and Eukaryotes dates much further back, approximately two billion years. We are curious to analyze the life style and cellular structure of Lokiarchaeota, as it might give even more exciting insights into early evolution.”
—–
Follow redOrbit on Twitter, Facebook, Google+, Instagram and Pinterest.
Comments