635 million year old fungus-like microfossils ejected from the ice age we discovered

Microscopic image of fungal-like filamentous microfossils. Credit: Andrew Czaja of the University of Cincinnati.

When you think of fungi, what comes to mind may be an important ingredient in a recipe or their amazing ability to break down dead organic matter into important nutrients. But new research conducted by Shuai Xiao, a professor of geosciences with the Virginia Tech College of Science, and Tian Gaan, a Ph.D. The student at Geo Lab, highlights yet another important role that fungi have played in Earth’s history: helping the planet overcome the ice age.

A team of scientists from Virginia Tech, the Chinese Academy of Sciences, the University of Guizhou Education and the University of Cincinnati have discovered the remains of microfossil-like fungi that emerged at the end of an ice age about 635 million years ago. It is the oldest terrestrial fossil ever. To put this in perspective, this microfossil makes the oldest dinosaur nearly three times as likely.

Their findings were published in Nature communication On 28 January.

The fossil was found in small cavities within the well-studied sedimentary dolostone rocks of the Loverost Daushantuo Formation in South China. Although the Doushantuo Formation has provided a plethora of fossils to date, researchers did not expect to find any fossils towards the lower base of the Dolostone.

But against all odds, Gan found some long, thread-like filaments – which were one of the key features of the fungus.

“It was an accidental discovery,” Gan said. “At the time, we realized that this could be the fossil that scientists have been looking at for a long time. If our explanation is correct, it would be helpful to understand archaeological changes and early life development.”

This discovery is important for understanding many important points in the history of the entire Earth: the Ediacaran period and the terrestrialization of fungi.

When the Ediacaran period began, the planet was recovering from a catastrophic ice age, also known as “snowball earth”. At that time, the ocean surface was frozen to a depth of more than a kilometer and it was an incredibly harsh environment for almost any living organism, except for the few microscopic lives that succeeded. Scientists have long wondered how life ever returned to normalcy – and how the biosphere was able to grow larger and more complex than ever before.

With this new fossil in hand, Tian and Xiao are certain that the inhabitants of these microscopic, low-profile caves played many roles in the repair of terrestrial environments in Ediacaran times. One role involved his formidable digestive system.

The fungus has a unique digestive system that plays an even greater role in cycling of important nutrients. Using enzymes secreted in the environment, terrestrial fungi can chemically break down rocks and other hard organic materials, which can then be recycled and exported to the ocean.

“Fungi have a reciprocal relationship with plant roots, which helps them mobilize minerals such as phosphorus. Due to the relationship of terrestrial plants and important nutritional cycles, the biochemical weathering of terrestrial fungi, the global biochemical cycle, and Has a driving effect. Ecological interactions, “Gan said.

Although previous evidence stated that terrestrial plants and fungi formed a symbiotic relationship about 400 million years ago, this new discovery recalculates the time these two states colonized the land.

“The question was: were there fungi in the terrestrial area before the rise of terrestrial plants”, said Xiao, an affiliated faculty member of the Frylin Life Sciences Institute and the Global Change Center. “And I think our study suggests yes. Our fungal-like fossil is 240 million years older than the previous record. Thus, it is, by far, the oldest record of terrestrial fungi.”

Now, new questions have arisen. Since the fossil filaments were with other fossils, Gan set out to trace their old relationship.

“One of my goals is to stop the phytolanetic exertion of these other types of fossils that are associated with fungal fossils,” Gan said.

Xiao is thrilled to tackle the environmental aspects of these microorganisms. Sixty years ago, some believed that microorganisms such as bacteria and fungi could be preserved as fossils. Now that Xiao has seen them with his own eyes, he plans to learn more about how they have frozen over time.

“It is important to always understand organisms in the context of the environment,” Xiao said. “We have a general idea that they lived in small cavities in the dolostone rocks. But little is known about how they actually lived and how they were preserved. Anything like a fungus that has no bones or shells. Are, can be preserved in the fossil record.? “

However, it cannot be said with certainty that this fossil is a definite fungus. While there is a substantial amount of evidence behind this, investigations into these microfossils continue.

“We want to leave things open to other possibilities as part of our scientific investigation,” Xiao said. “The best way to plant it is that perhaps we have not ruled out that they are fungi, but they are the best explanation we have at the moment.”

Three different groups and labs at Virginia Tech were critical to the identification and timestamping of this fossil. The Confocal Laser Scanning and Microscopy Lab at the Fralin Life Sciences Institute helped Tian and Xiao perform preliminary analysis that prompted further investigation at the University of Cincinnati.

The Department of Biological Sciences Massey Herbarium, which has more than 115,000 specimens of vascular plants, fungi, bryophytes, and lichens, provided modern fungal specimens compared to fossils.

The team called on technicians to perform geochemical analysis using secondary ion mass spectrometry, ionizing nanomoles of material from small areas that are the thickness of a hair strand, to the isotopic abundance of sulfur-32 and sulfur-34. To analyze. Understand fossil environment.

Advanced computerized tomography was important for achieving 3-D morphology of filaments, which are only a few micrometers thick. And the combination of focused ion beam scanning electron microscopy and transmission electron microscopy allowed researchers to cut specimens with surgical precision and a closer look at each nanometer of filaments.

“It was not a single person or a single lab that did this work,” Xiao said.

Xiao also emphasized the importance of interdisciplinary research in this study and many others.

“It is very important that the next generation of scientists be encouraged to be trained in an interdisciplinary light because new discoveries are always at the interface of different fields,” Xiao said.

I’m an evolutionary biologist – here’s why this ancient fungal fossil discovery is very revealing

more information:
Nature communication (2021). DOI: 10.1038 / s41467-021-20975-1

Provided by Virginia Tech

Citation: 635 million year old fungus-like microfossil that drove us out of the discovered ice age (2021, 28 January) Retrieved 28 January 2021 from https://phys.org/news/2021-01-million-year-old did. -fungi-like-microfossil-bailed-ice.html

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