Researchers Discover a Puzzling New Organism Resembling a Living Sun

Researchers have identified a new microorganism, Solarion arienae, which retains traces of early mitochondrial evolution, a feature critical to the development of eukaryotic life. Scientists believe that early eukaryotes, including Solarion, originated from prokaryotic cells merging and eventually forming a nucleus.

Genetic studies indicate that Solarion may possess a pathway inherited from an ancient cellular merger. The organism has striking protruding appendages tipped with spherical structures, giving it a sun-like appearance, reminiscent of a cartoon Sun or a retrofuturistic chandelier. This discovery has the potential to reshape our understanding of eukaryotic evolution that occurred billions of years ago.

Protists were the first eukaryotes, distinguished by having a nucleus, unlike their prokaryotic ancestors. Eukaryotic cells likely arose from symbiotic mergers of prokaryotes, with mitochondria themselves possibly being ancient bacteria incorporated into other cells. These early eukaryotic cells eventually led to multicellular life.

Solarion represents a new genus, species, and phylum within the recently defined eukaryotic supergroup Disparia. Contrary to previous assumptions that early eukaryotes were metabolically limited, Solarion retains remnants of mitochondrial pathways, preserved from bacteria that existed long before dinosaurs appeared.

Biologist Matthew Brown of Mississippi State University, who discovered the species, explained that these molecular remnants provide valuable insights into the origins of mitochondria. Solarion arienae expands our understanding of early eukaryotic evolution and sheds light on the metabolic foundations of ancient cells, he noted.

These ancestral features in protists offer clues about cell structure and metabolism. Mitochondria serve as cellular energy hubs, breaking down nutrients, managing waste, and supporting cellular homeostasis. They also help cells respond to stressors like nutrient shortage or DNA damage.

Solarion was found unexpectedly in a lab culture of anaerobic marine protozoans. Culturing revealed it as a eukaryote closely related to Meteora sporadica. Its rarity may be due to either its elusive habitats or specific ecological preferences.

The organism exhibits two distinct life stages. In its most common Sun form, it uses radiating appendages, or extrusomes, to capture bacteria. In a second phase, it loses these structures and becomes an oblong flagellate capable of movement. Some flagellate cells can revert to the sun-like morphology.

Structurally, Solarion has a single centriole, unlike most eukaryotes that have two. The spherical tips of its extrusomes, called kinetocysts, are used to catch bacteria. While Meteora sporadica shares a similar morphology, Solarion has one orb per appendage instead of several. Both now form the new phylum Caelestes.

Despite billions of years of evolution, Solarion retains rare mitochondrial genes, encoding proteins typically found in eukaryotic nuclei. Its SecA pathway, unusual for residing in mitochondria rather than the cytoplasm or cell membrane, may reflect a repurposed ancestral function.

While the full implications of Solarion, the Caelestes phylum, and Disparia are still being explored, researchers are eager to uncover more about early eukaryotic evolution that eventually led to humans and all multicellular life. Brown emphasized that ongoing research and improved sampling methods will help clarify Disparias position in the tree of life.

Author: Logan Reeves