Cells with bare minimum genes can still evolve as fast as normal cells: study Premium

Researchers from Indiana University, Bloomington, studied a synthetically designed ‘minimal’ cell, containing only genes essential for survival, and found that it could evolve as fast as a normal cell. This “demonstrates the capacity for organisms to adapt, even with an unnatural genome that would seemingly provide little flexibility,” said Jay Lennon, a professor at Indiana University, whose team made the discovery.

Around 5,000-10,000 years ago, dairy farming changed some people’s DNA. As they began to drink milk, human adults’ genes began to accumulate mutations that would help them digest it.

Such mutations help an organism evolve. Complex organisms like humans contain thousands of genes, most of which are not essential for survival. Mutations in these genes are not lethal. As a result, evolutionary forces can act on these genes, and any beneficial mutation becomes more abundant over time.

But what if a simple organism contained only those genes essential for its survival? Any mutation in such an organism could lethally disrupt its cellular functions. How will evolutionary forces act on the genome of such an organism when it contains so few targets on which selection can act?

Researchers from Indiana University, Bloomington, used a synthetically designed minimal cell containing only genes essential for survival to answer this question. Their findings, published recently in the journal Nature, showed that even such a cell can evolve as fast as a normal cell.

This “demonstrates the capacity for organisms to adapt, even with an unnatural genome that would seemingly provide little flexibility,” said Jay Lennon, a professor at Indiana University, whose team made the discovery.

Dr. Lennon’s team used a synthetic version of Mycoplasma mycoides, a microbe commonly found in the guts of goats and cattle. They created a stripped-down minimal cell (JCVI-syn3.B) with only 493 genes, down from the 901 genes in the non-minimal strain (JCVI-syn1.0). Although the minimal cells were alive and could reproduce, genome minimisation also made them sick, reducing their fitness by over 50%.

To test whether these minimal cells responded differently to the forces of evolution compared to non-minimal cells, the team grew them separately in a liquid medium, transferring a small, fixed amount of the population into fresh medium every day. They did this for 300 days, allowing the bacterial lineage to pass through 2,000 generations (equivalent to about 40,000 years of human evolution).