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Home / Science / Amoebae diversified at least 750 million years ago, far earlier than expected – ScienceDaily

Amoebae diversified at least 750 million years ago, far earlier than expected – ScienceDaily



Brazilian researchers have reconstructed the evolutionary history of amoebae and demonstrated that at the end of the Precambrian period, at least 750 million years ago, life on earth was much more diverse than suggested by classic theory.

The study, which what supported by Sao Paulo Research Foundation – FAPESP, revealed eight new ancestral lineages of Thecamoebae, the largest group in Amoebozoa. Thecamoebians are known as testates because of their hard outer carapace or shell.

In this study, published in the journal Current Biology researchers affiliated with the University of Sao Paulo's Bioscience Institute (IB-USP) in Brazil, in partnership with colleagues at the Mississippi State University in the United States, uses innovative techniques to reconstruct the phylogenetic (evolutionary) tree of Thecamoeba, which belongs to the order Arcellinida.

The new phylogenetic tree was created using mathematical algorithms and the transcriptomes of 1

9 arcellinids found in nature today. The researchers thus established the morphology and composition of the fossil record.

750 million years ago, ancestors of the Camoebians were already evolving.

"We reached our conclusions using a combination of two major scientific areas – paleontology and phylogenetic systematics, the field within biology that reconstructs evolutionary history and studies the patterns of In this way, we were able to untangle one of the knots in evolutionary theory about life on the planet, "said Daniel Lahr, a professor at IB-USP and lead author of the article.

Reclassification of Amoebozoa

The researchers completely dismantled the previous classification of the Camoebians. [from 750 million years ago] of arcellinids about which nothing was known, "Lahr told.

The old thecamoebian classification was based on shell composition. However, they were divided into agglutinate and organic.

The old classification, he added, had been questioned for several years, but more evidence what needed to demolish it. The genetic community suspected that the arcellinid testate amoebae had emerged and evolved to diversify some 750 million years ago

Past and future

According to Lahr, the study presents a different view of how microorganisms evolved on the planet. The late Precambrian was considered a period of low biotic diversity, with only a few species of bacteria and some protists.

"It was in this period 800 million years ago that the oceans became oxygenated The study published in Current.

The study published in Current Biology, he added, on a detail of this question. "What's more, geophysicists are discovering that this process has slowed down and may have lasted 100 million years or so," he said. 19659003] However, scientists do not know what pressure triggered this oxygenation. One way to resolve the competition for another is to get more and more multicellular, "Lahr said.

The study has also contributed to a better understanding of today's climate change. "We began to understand in more depth how this microbial life affects the planet in several ways," Lahr said. This is one of the largest glaciation events ever. "

According to Lahr, these changes may have had biological origins , "We are currently experiencing," he said.

In rock

In addition to the discovery of greater diversity in the Precambrian, the study also establishes the morphology of the ancestors of thecamoebians to establish the vase-shaped microfossils (VSMs).

VSMs are presumed to be fossils of testate amoebae. They are unicellular and eukaryotic and have an external skeleton. Significant diversity of VSMs has been documented for the Neoproterozoic era, which spanned between 1 billion and 541 million years ago, and what the terminal era of the Precambrian.

"The microorganisms evolved on the planet Although it is possible to compare their chemical composition, which in this case are especially well preserved , with those of current thecamoebians reconstituted by big data, "said Luana Morais, a postdoctoral researcher with a scholarship from FAPESP and coauthor of the article.

Innovative techniques

In addition to the lacquer of DNA-containing fossils, the researchers facing another obstacle in reconstructing the phylogenetic tree: thecamoebians can not be cultured in the laboratory, and gen

The solution to this problem is to use the single-cell transcriptome technique to analyze phylogenetics (instead of gene expression, its normal application). "We sequenced whole transcriptomes of arcellin amoebae using live samples," Lahr explained.

The researchers used transcriptome-based methodology to capture all of the messenger RNAs from each individual cell and "This yielded several thousand genes and some 100,000 amino acids sites, or 100,000 datapoints giving the phylogenetic tree, which had never been seen before." convert them into a sequenceable complementary DNA library.

"Our research is fundamentally on single cell transcriptomics, in which our lab is one of the worldwide pioneers," Lahr said.

In this study, the researchers selected 250. "This is a revolutionary technique in this field because it allows us to find a single [unicellular] amoeba, isolate and clean it, and perform all the procedures for the procedure to sequence the whole transcriptome." genes to construct the phylogenetic tree. "It's not good looking at just one cell when you're studying expression, because the resolution will be insufficient," Lahr said. Thus, it is possible to use this technique, which has originally been developed for tumor cells, and adapt it It is much larger than a tumor cell. "

Before the technique was developed, only organisms grown in the laboratory could be sequenced. It's estimated that only 1% or less of all biodiversity is cultivable, "Lahr said.


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