Along the western coastline of Australia resides a portal to our history: the stromatolites and microbial mats of Gathaagudu (Shark Bay).
To the uninformed observer, these formations might appear as mere aggregations of rocks and viscous material; however, they are, in actuality, densely populated with microbial organisms. These stromatolites serve as living testaments to ancient ecosystems that flourished on Earth eons ago.
Venturing through them evokes a sensation of traversing backward through time. Indeed, the initial release of oxygen into the atmosphere of early Earth is thought to have originated from primitive stromatolites. One could argue that our very existence is indebted to these rocky structures.
Consequently, what further historical revelations might these ecosystems impart? Through extensive investigations spanning decades, we have gained insight into how early lifeforms established their presence within these “living stones.”
Most recently, our research consortium undertook a monumental genealogical exploration: the pursuit of our ancestral microbial predecessors, the Asgard archaea.
In a recent publication, released today in the esteemed journal Current Biology, we delineate our findings from this quest, which yielded a pivotal discovery potentially illuminating the evolutionary trajectory of complexity in terrestrial life.
The cellular building blocks of complex organisms
The Asgard archaea derive their nomenclature from figures in Norse mythology. This intriguing group of microorganisms occupies a critical juncture in the evolutionary history of life, preceding the emergence of the sophisticated cells that constitute plants and animals, known as eukaryotes.
Compelling evidence indicates that Asgard archaea are the closest extant relatives to eukaryotes. It is hypothesized that on primordial Earth, the advent of the first eukaryotes resulted from a symbiotic union between an ancestral Asgard archaeon and a bacterium.
This established an ancient symbiosis. They engaged in resource exchange and direct physical contact, leading to the formation of the earliest complex cells. Mirroring a narrative of two disparate lineages uniting, Asgard archaea and bacteria transcended their former biological boundaries.
However, a concrete model illustrating this transformative process remained elusive—until now.
A reflection of Earth’s ancient past
Our investigative unit utilized the microbial mats of Shark Bay as a foundational source to cultivate these ancient microorganisms. Our team is among a select few globally to have achieved this, a feat accomplished through years of dedicated research and meticulous cultivation of the Asgards by a committed cohort of graduate students, akin to nurturing offspring.
Crucially, the Asgards were not isolated. We discovered them in close association with a sulfur-reducing bacterium. Could this consortium represent a paradigm for the genesis of complex life on early Earth?
Our initial approach involved sequencing the Asgards’ genetic material to meticulously decipher their biochemical mechanisms at the genomic level. Furthermore, we employed artificial intelligence to simulate protein functionalities in a pre-eukaryotic environment. The data strongly suggested a mutualistic exchange of nutrients between these two microbial entities, indicative of cooperation.
Nevertheless, we sought a more profound understanding. What is the morphology of our ancient microbial ancestors? To address this, we employed electron cryotomography, a high-resolution imaging technique enabling the visualization of cellular structures at the nanometre scale.
Through this advanced methodology, we established, for the first time, direct interfacial contact between an Asgard archaeon and a bacterium. The observation of interconnected nanotubes linking the two organisms offers a potential glimpse into the ancient interactions that may have precipitated the vast diversification of complex life as we comprehend it today.
Integrating Western scientific methodology with Indigenous knowledge systems
This represented a significant scientific breakthrough—a discovery rooted in Gathaagudu, a locale recognized as a World Heritage Site, holding profound environmental and cultural importance.
The Indigenous inhabitants of Gathaagudu have a history stretching back over 30,000 years. Our intention was to acknowledge and honor the linguistic heritage of the Malgana people, one of the ancestral custodians of Gathaagudu. Furthermore, we aimed to forge a meaningful synthesis between Western scientific inquiry and Indigenous Knowledge.
In furtherance of this objective, and in close collaboration with Kymberley Oakley, a leading authority on the Malgana language, and esteemed Aboriginal elders, a designation was bestowed upon our novel Asgard archaeon, drawing from the Malgana lexicon: Nerearchaeum marumarumayae.
The specific epithet, marumarumayae, is derived from the Aboriginal language of the Malgana people and translates to “ancient home,” signifying the profound antiquity of stromatolites in Earth’s history.
The incorporation of Aboriginal language into the nomenclature of our newly identified microbe represents a fitting nexus between the distinct cultural legacy of Indigenous Australians and the ancient microorganism discovered, which finds its habitat within the mats of Gathaagudu.
Gathaagudu faces substantial peril due to global environmental shifts, including escalating heatwaves, intensified cyclonic activity, and anthropogenic pressures. Among the invaluable assets requiring preservation and conservation are the profound Aboriginal connections to this land, as well as the enduring evolutionary chronicles etched in its lifeforms.
Through our research, we have gained a profound vista into our past.
Perhaps akin to the Montagues and Capulets of Shakespearean fame, we observe distant microbial lineages converging, bridging their inherent divisions, and ultimately giving rise to the primordial eukaryotes that eventually led to our own existence—a delicate and vital branch on the grand evolutionary tree of life.
