A creature that broke the law of biology has been found in an Oxford pond

Scientists from the Earlham Institute and the University of Oxford discovered a microorganism in an ordinary pond that violated one of the fundamental rules of genetics by rewriting the meaning of "stop signals" in DNA. The results of this unique study were published in the journal PLOS Genetics.

The genetic code is often compared to an instruction manual for assembling a protein. It contains three special combinations of "letters" — stop codons. They function as a signal meaning "the protein is complete, there is nothing more to build." This principle was considered universal for all life on Earth. However, in the DNA of the discovered ciliate, two such signals unexpectedly acquired a different meaning. Instead of stopping, they began to point to specific amino acids — the building blocks of protein. In simpler terms, where the cell was supposed to say "stop," it continued reading the instructions further.

The subject of the study was a microscopic organism of the species Oligohymenophorea sp. PL0344, which the specialists had initially collected to test a method of reading DNA from a single cell. It turned out that it had only one functioning "stop signal" remaining, while the other two had ceased to halt protein synthesis and began encoding amino acids instead. This task was taken on by special translator molecules: they recognize the code and insert the appropriate building block.

"This shows how little we know about protist genetics and how much more flexible life is than textbooks suggest," noted researcher Dr. Jamie McGowan.

Historically, science has made discoveries by relying on organisms that are easy to grow in the laboratory. The discovered ciliate did not survive under laboratory conditions, but the new DNA reading technology was successfully applied directly to material from the natural environment. Soon, similar genetic anomalies were identified in marine microorganisms from Arctic waters. This proved that evolution rewrites the basic vocabulary of life not just in one unique location.

Understanding how a cell manages to safely change the meaning of "periods" in DNA will help bioengineers in the future create artificial organisms with similar properties.