In the laboratory, scientists assembled a cell from non-living components, and for the first time it passed through the entire cycle of growth and division. The system, built from scratch, grew, copied its own DNA, and split into two parts. This is the most convincing evidence so far that the boundary between the living and the non-living can be crossed artificially.
Built from Scratch
Project leader Kate Adamala, a synthetic biologist at the University of Minnesota, and her team assembled each element of the system separately. The foundation consisted of liposomes, empty bubbles made of a lipid membrane that replaced the cell оболонка. Wait, correction: that should be “cell membrane.”
Inside them, the researchers placed a DNA-copying system and a set of 36 enzymes capable of reading genetic information and synthesizing proteins. These two mechanisms had to be coordinated for a long time by adjusting the concentrations of the components one by one.
The finished genome did not contain everything necessary for the cell, so the researchers prepared separate liposome containers with sugar, lipids, and enzymes, as well as more complex molecules such as tRNA and ribosomes. When such a bubble came into contact with the cell, their membranes fused, and the contents passed inside.
The Barrier of Division
Synthetic cells in previous attempts were able to grow and copy DNA, but they always stopped at the same barrier. A natural cell reorganizes its cytoskeleton, a network of protein filaments that supports its shape, and thanks to this it splits into two parts. Reproducing such a complex mechanism artificially had, until recently, proved impossible.
Kate Adamala found a solution in a paper by theoretical physicist and biophysicist Reinhard Lipowsky of the Max Planck Institute of Colloids and Interfaces. Protein markers on the membrane attract other proteins, which cluster together and physically bend the membrane, forcing it to divide. After several attempts, this same mechanism worked in the synthetic system as well.
Not Yet a Living Cell
As Quanta Magazine reports, the resulting system is not alive in any sense of the word. It cannot survive without a constant supply of nutrients and ribosomes, the molecular machinery that synthesizes proteins.
It has no protective mechanisms of its own, and its waste-removal system is imperfect. The work was posted as a preprint on biorxiv.org on July 2 and has not yet undergone peer review.
Jack Szostak of the University of Chicago, who was Kate Adamala’s scientific advisor, noted that the cell’s inability to produce these components on its own limits its capacity for growth and repeated reproduction. Kate Adamala herself acknowledges that the system lacks a cytoskeleton, and that division currently requires a great deal of time and energy precisely because of its absence.
The Boundary of the Definition of Life
At the same time, the team tested whether the system could develop according to the laws of natural selection. Cells whose size was artificially increased produced more offspring and gradually came to dominate the population. This became the first step of such a process. However, this is not yet true Darwinian evolution, because the differences necessary for selection were created manually by the researchers rather than arising through random mutations, since the enzyme that copies DNA works too accurately.
In astrobiology, NASA ’s working definition has been used for decades, describing life as a chemical system capable of Darwinian evolution. This is the criterion taken into account when searching for life on Mars, the moons of Jupiter or Saturn, and exoplanets.
The synthetic cell does not yet meet this definition, because it does not evolve on its own. However, the experiment shows that the basic functions of living things, such as growth and division, can be reproduced from simple molecules. Such a process may once have turned non-living chemistry into the first cells on Earth, just as it may have on other planets in the Universe where the necessary conditions exist.
