Researchers Found Microbes with Mixed Membranes in the Black Sea

Discovery of microbes with mixed membranes sheds new light on early evolution of life

A recent study indicates that more complex life-forms, such as humans, evolved from something known as a symbiosis event of Bacteria and another single-celled organism, the Archaea. 

Proof of a transition period in which those two organisms mixed where nowhere to be found. But now, researchers found the missing key.

Researchers discovered microbes in the Black Sea’s deep waters that can produce membrane lipids, more like a layer that covers a cell like a skin. Their origin is unexpected. Here is what you need to know.

Transforming Skins

Cells are enclosed by a layer of membrane lipids that shield them from fluctuations in their environment, such as the temperature. The process is similar to how our skin changes when we’re exposed to the sun or when we’re cold. 

Laura Villanueva, the lead author of the study and a NIOZ senior scientist, released the first statements. She explained that when a cell dies, the lipids begin to preserve like fossils and hold old information on Earths’ ancient environmental conditions.

Our “tree of life” contains simple and small cells (Bacteria and Archaea) and more complex cells known as Eukaryotes, including humans and animals. The Eukaryotes and Bacteria share a similar lipid membrane.

“[…] difference in membranes between Bacteria and Eukaryotes on the one hand and Archaea on the other, is believed to have happened after the emergence of Bacteria and Archaea from the last universal cellular ancestor,” detailed Villanueva.

The Secrets of the Black Sea

A leading theory is that Eukaryotes evolved from a symbiosis event between bacterial and archaeal cells in which the second was the host. The question here is how such a thing works when their “skins” are so complex and share no sign of common lineage? 

Villanueva and her team discovered a possible missing key in the Black Sea. There, a rich group of bacteria flourishes, absent of oxygen and with high sulfide concentration. The team found that the group’s genetic material didn’t only transport pathway genes for bacterial lipids but also archaeal ones. 

Such a strange thing was also discovered in the genetic material of other, closely related Bacteria; it supports the theory that this ability to make “mixed” membranes is more widespread than previously believed. 

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