Nobody knows how the first living beings appeared on the planet. About 3 billion years ago, a clump of dead matter began to reproduce itself by producing copies of itself. It was the first living being.
Biology, through the process of natural selection, is able to explain how all living beings existing today, from a bacterium to a whale, evolved from this first living being. But no theory explains how dead matter turns into living matter. So, without knowing how these first living beings emerged and what they looked like, scientists can only attempt to understand this process by creating a living being in the laboratory.
It’s a fascinating but thankless area of biology, where progress has been slow. And worse, we are far from the final goal. But now an important step has been taken, a cell has been created that is not yet a living being, but already has many properties of a living cell.
Scientists began construction by producing a coacervate. When you mix two aqueous solutions (eg beer and wine), the mixture is usually a homogeneous liquid. But depending on what is present in the two solutions, sometimes one of the liquids forms tiny spheres surrounded by the other liquid. It is a coacervate.
These coacervate pellets were used as the basis for constructing the artificial cell. In the next step, the scientists added two types of bacteria that stuck to the outside of the pellets. Then they put in a substance that kills bacteria by breaking the membrane covering them and found that the ruptured membrane of hundreds of bacteria fuse together and form an artificial membrane around the pellets.
Also, all of the content that was inside the bacteria ended up getting inside the coacervate pellets. The end result is spheres covered with a membrane and containing all the components necessary for the functioning of a living cell. But all the components were mixed there and we know that DNA is normally aggregated in the cell nucleus.
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To try to form a nucleus, the scientists added proteins that bind to DNA and observed that the DNA clumped together into something similar to a nucleus. It still lacked certain properties present in truly living cells: a source of energy and the ability to change shape. The ability to change shape was obtained by adding proteins that form the skeleton of living cells (like actin).
To produce energy, they put inside bacteria modified to produce energy from sugars. As you can see, building this artificial cell is akin to baking a cake, you add the components in the correct order and quantity to achieve the desired characteristics.
After building this artificial cell, scientists devoted themselves to studying its behavior. They observed that it is able to produce most of the chemical reactions existing in a living being, grows larger over time, changes shape like any living being, but is not able to divide. Its behavior is very similar to that observed in an amoeba.
Scientists have observed in these cells seven properties present in living beings: they have a membrane all around them, an internal environment where the components are isolated from the external environment and are in high concentration, they are capable of carrying out sequential chemicals, they are able to synthesize proteins, have sub-compartments where genetic material (DNA) and energy production are located, have a cytoskeleton and are capable of adopting several forms. They still cannot be considered living beings because they are not able to reproduce, the most striking characteristic that separates inanimate matter from living matter.
These experiments demonstrate that we are slowly moving towards producing a living being from inanimate components. But progress is slow and we are still far from being able to create a living being. When this happens, we will be able to say that we understand how life originated on the planet, how it evolved and spread, organizing itself into the complex ecosystems that exist today.
More information: Living material assembly of bacteriogenic protocells. nature