Protocells created in the conditions of deep-sea hydrothermal vents

Hydrothermal vent in the Urashima site (Photo courtesy Submarine Ring of Fire 2014 - Ironman, NSF/NOAA, Jason, Copyright WHOI)
Hydrothermal vent in the Urashima site (Photo courtesy Submarine Ring of Fire 2014 – Ironman, NSF/NOAA, Jason, Copyright WHOI)

An article published in the journal “Nature Ecology & Evolution” reports the creation of protocells in warm and alkaline salt water that replicate the conditions of the hydrothermal vents existing in deep seas. A team of researchers led by University College London (UCL) took a step forward in research into the origin of life on Earth by bringing new clues that hydrothermal vents are the place where the first life forms emerged. In fact, they proved the possible formation of protocells starting from compounds existing in that environment and in those environmental conditions.

Protocells, or protobionts, are not yet biological structures that are formed by various molecules enclosed in a membrane with a double lipid layer or a similar structure. They could represent a key passage between complex organic molecules and life forms but so far researchers managed to obtain their formation starting from fatty acids only in well controlled conditions in cold fresh water.

Hydrothermal vents are environments in which sea water comes into contact with minerals coming from the Earth’s crust, reacting to create a warm and alkaline environment containing hydrogen. This process creates mineral-rich chimneys with alkaline and acid fluids, providing an energy source that favors chemical reactions between hydrogen and carbon dioxide to form increasingly complex organic compounds. For this reason, they have long been considered among the most promising among the possible places of origin of life on Earth. Despite this, attempts to obtain the formation of protocells in environments that replicated the hydrothermal vents had failed.

Dr. Sean Jordan of UCL, the first author of this new research, explained that he and his colleagues identified a flaw in previous work in the fact that they used a small number of types of molecules, mostly with fatty acids of the same size, whereas in natural environments one can expect to find a wider variety of molecules. This time, the researchers tried to create protocells with a mixture of different fatty acids and fatty alcohols that wasn’t used before.

The result was the discovery that molecules with longer carbon chains needed heat to form a vesicle (protocell). An alkaline solution helped those vesicles maintain their electrical charge. An environment with salt water also proved useful since the fat molecules banded more tightly in a salty fluid, forming more stable vesicles. Dr. Sean Jordan explained that he and his colleagues created one of the essential components of life in conditions that reflect the ancient environments more closely than many other lab studies.

Professor Nick Lane of UCL, who led this research, explained that the discoveries made with his colleagues add weight to the theory that sees hydrothermal vents among the most promising places for the beginning of life with solid experimental evidence. He also offered some reflections on the possible implications for life in the universe considering that even in the solar system there are hydrothermal vents in places other than Earth, to be precise under the icy crust of Jupiter’s moon Europa and under the icy crust of Saturn’s moon Enceladus.

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