Gas bubbles in the pores of rocks were a nursery for life on early Earth
Where and how did life on early Earth begin over 3.5 billion years ago from non-living chemicals? A key necessity for the first cells on Earth is the ability to create compartments and evolve to facilitate the first chemical reactions. Membrane-less coacervate microdroplets are excellent candidates for describing protocells, with the ability to divide, concentrate molecules, and support biochemical reactions. Scientists have yet to show how these microdroplets could have evolved to begin life on earth. Researchers at the Max Planck Institute of Molecular Cell Biology and Genetics in Dresden and the Center for NanoScience (CeNS) at the Ludwig-Maximilians-Universität (LMU) in Munich now demonstrate for the first time that the growth and division of membrane-free microdroplets is possible in an environment similar to gas bubbles in a heated rock pore on early Earth. Suggesting that life may have originated there.
The team around Dora Tang, research group leader at the Max Planck Institute for Cell Biology and Molecular Genetics, showed in 2018 that simple RNA is active in membrane-less microdroplets, allowing a suitable chemical environment for the beginning of life. These experiments were conducted in a simple aqueous environment, where the competing forces were balanced. Cells, however, need an environment where they can constantly divide and evolve.
To find a more suitable scenario for the origin of life experiences, Dora teamed up with Dieter Braun, professor of systems biophysics at LMU Munich. His group developed conditions with an unbalanced environment that allow multiple reactions in a single setting and where cells could evolve. These cells, however, are not like the cells we know today, but rather like precursors of today’s cells, also known as protocells, made up of membrane-less coacervates.
Water containing pores with gas bubble
The environment, created by the Braun lab is a likely scenario on early Earth, where porous rocks in water near volcanic activity have been partially heated. For their experiments, Dora and Dieter used pores containing water with a gas bubble and a thermal gradient (a hot pole and a cold pole) to see if the protocells would divide and evolve. Alan Ianeselli, the study’s first author and doctoral student in Dieter Braun’s lab, explains that they “knew that the interface of gas and water attracted molecules. Protocellules localize and accumulate there, and assemble into larger ones. This is why we have chosen this particular framework. “
The researchers observed that molecules and protocells went to the gas-water interface to form larger protocells from sugar, amino acids and RNA. Alan continues that they “also observed that protocells were able to divide and fragment. These findings represent a possible mechanism for the growth and division of membranes without a membrane on early Earth.” In addition to division and evolution, the researchers found that as a result of the thermal gradient, several types of protocells of different chemical composition, size and physical properties were formed. Therefore, the thermal gradient in this environment could have resulted in an evolutionary selection pressure on the non-membrane protocells.
Dora Tang and Dieter Braun, who oversaw the study, summarize: “This work shows for the first time that the gas bubble in a heated rock pore is a compelling scenario for the evolution of membrane-less coacervate microdroplets on the Primitive earth. Future studies could focus on more possible habitats and explore other conditions for the emergence of life. “
The research was published in Chemistry of nature.
Origin of life in protocells without membrane
Dieter Braun, Non-equilibrium conditions inside rock pores lead to fission, maintenance and selection of coacervate protocells, Chemistry of nature (2021). DOI: 10.1038 / s41557-021-00830-y.
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