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Researchers led by evolutionary scientist Jay T. Lennon have been examining a synthetically developed minimal cell that lacks everything but the bare minimum of genes. The research team discovered that the streamlined cell can evolve at the same rate as a regular cell, proving that organisms can adapt even when presented with an artificial genome that appears to allow limited room for flexibility
A report published in Nature provides further information about the investigation. Ph.D. candidate Roy Z. Moger-Reischer, who worked in the Lennon lab for the study’s time period, is the paper’s corresponding first author.
If there’s one thing we can take away from the course of evolution, it’s that life is inherently aggressive. Existence is set free. Life finds a way. It extends to new territories and it crashes through obstacles painfully, maybe even dangerously. This is according to Jeff Goldblum’s character, Ian Malcolm, in the 1993 film Jurassic Park, about the park with live dinosaurs.
Although there are no dinosaurs lurking in his lab, Professor of Biology in the College of Arts and Sciences at Indiana University Bloomington, evolutionary Lennon, and his colleagues have discovered that life does indeed find a way.
Lennon comments that it seems there’s something about life that’s really robust. The researchers can simplify it down to just the bare essentials, but that doesn’t stop evolution from going to work.
Synthetic organism Mycoplasma mycoides JCVI-syn3B was utilized in the research conducted by Lennon’s group. This organism is a reduced form of the bacterium M. mycoides, which is often found in the digestive tracts of goats and other similar animals. Because it has relied on its host for so long for nutrition, the parasitic bacteria has lost many of its genes throughout the millennia.
California’s J. Craig Venter Institute went it farther with their research. In 2016, they took the naturally occurring M. mycoides genome and removed 45 percent of its 901 genes, leaving only the bare minimum for autonomous cellular life. The genome of M. mycoides JCVI-syn3B has just 493 genes, making it the smallest of any known free-living organism. The genomes of many animals and plants, meanwhile, have about 20,000 genes.
In theory, the smallest possible living being would have only the needed amount of genes and no redundant systems. Limits on evolution are set by the fact that every mutation in such an organism might fatally impair one or more biological processes. Reduced adaptability potential is a consequence of positive selection acting on fewer sites in organisms with simplified genomes.
Lennon and coworkers wanted to know how a minimal cell would respond to the forces of evolution over time, especially given the limited supplies upon which natural selection could operate and the uncharacterized input of new mutations, despite the fact that M. mycoides JCVI-syn3B could grow and divide in laboratory conditions.
For M. mycoides JCVI-syn3B, each and every single gene in its genome is important, as stated by Lennon. It’s possible that its evolutionary potential is limited since there’s no place for mutations.
The high mutation rate of M. mycoides JCVI-syn3B was confirmed by the study’s authors. They let it thrive in the lab for 300 days, which is the same as 2,000 generations of bacteria or almost 40,000 years in human terms.
Experiments were subsequently created to see how the 300-day-evolved minimal cells responded in comparison to the non-minimal M. mycoides and a strain of minimal cells that had not undergone 300 days of evolution. The researchers combined the same amounts of each strain into a single test tube for the comparative testing. The strain that thrived in that particular setting eventually became the norm.
They discovered that the non-minimal form of the bacteria outperformed the less developed minimum form. However, the 300-day-evolved minimum bacterium performed exceptionally well, regaining all of the fitness it had lost because of genome streamlining. The genes that underwent the most dramatic changes during the course of evolution have been pinpointed. Some of these genes had a role in creating the cell’s outer membrane, while others’ roles are unclear.
The ability to treat clinical pathogens, maintain host-associated endosymbionts, improve engineered microorganisms, and even better understand the origin of life all hinge on our ability to understand how organisms with simplified genomes overcome evolutionary challenges.
Natural selection has been shown by Lennon and his team to swiftly optimize fitness in the smallest autonomous creature, which has implications for the development of cellular complexity. Simply said, it’s proof that life always finds a way.
Sources:
Moger-Reischer, R.Z., Glass, J.I., Wise, K.S. et al. Evolution of a minimal cell. Nature (2023). https://doi.org/10.1038/s41586-023-06288-x
https://phys.org/news/2023-07-artificial-cells-life.html
