“Hair” formed by bacteria have contributed to the development of complex life under the sea – 06/02/2021 – Reinaldo José Lopes

Let the reader, if they can, imagine the ocean floor 563 million years ago – before whales, before the great aquatic reptiles of the age of the dinosaurs, even before the trilobites (those extinct invertebrates that look like a wrinkled crab with a flying saucer). It’s not easy, I admit. However, researchers from Brazil and Canada used very subtle fossils to make this puzzle a little less hairy. Or hairier, to be precise.

It turns out that the fossils they examined suggest that at least part of the seabed at the time – in this case the part that was preserved in certain rocks of the interior of Santa Catarina – was covered with “giant” bacteria that resembled it the strands of hair. Taking advantage of the ocean’s particular geochemical conditions at the time, they may have even accelerated the development of the first complex life forms, which appeared and diversified simultaneously.

The results are described in an article that was recently published in the journal Proceedings of the Royal Society B. Signed by Bruno Becker-Kerber from UFSCar (Federal University of São Carlos) and the University of Poitiers together with colleagues from four years.Other institutions involved an analysis of more than 1,600 filamentous fossils that could reach a length of 4.4 cm, but were only 0.2 mm thick. That is, relatively long, but very thin (in the photos of the article, a pinhole is used for comparison, in a nice homemade touch).

The rocks with the fossils, which come from a side road between the cities of Apiúna and Subida (SC), correspond to the Ediacarano period, a phase in the earth’s history between 635 million years and 541 million years. This is the moment when, after a predominance of unicellular life forms that has lasted since the beginning of the planet, evolution finally begins to play with building multicellular bodies, as we do today.

Well, not exactly, to be honest. In Ediacaran, the beings of many cells do not look like almost anything that came after, with the possible exception of one or two marine invertebrates. Many have flat, disc-shaped shapes; others look like feathers stuck in the ocean floor; and there are also those that resemble a stack of cups joined together. The relationship between such creatures and the animals that appeared after that is still not 100% clear.

After analyzing the properties of the petrified filaments (such as the fact that they appeared to adhere to the ocean floor and were initially flexible), the researchers concluded that they most likely correspond to bacteria similar to those that exist today in certain aquatic environments. their cells normally use H2S (hydrogen sulfide) as an energy source.

Everything indicates that they formed their “wigs” in places on the boundary between depths with higher and lower oxygen levels in the water. They could serve as a food source for the strange Ediacaran invertebrates, but they would also remove much of the sulfur (corresponding to the S of the H2S formula) from the water, which is normally toxic to marine animals.

Hence, the researchers suggest that a close connection between sea hair and the oldest animals was important for the next steps in the history of life. Yes, this sea looked like a strange world – but it contained the seeds of the diversity that we still see around us today. We are a family business.

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