Researchers have discovered a previously unknown protist, Oligohymenophorea sp. PL0344, that uses a unique genetic code. Found in a freshwater pond in England, the organism interprets two standard stop signals as different amino acids, challenging evolutionary assumptions about how genetic instructions are translated into proteins.
Scientists Find Unusual Organism in an English Pond
While testing a DNA sequencing method on a sample collected from a freshwater pond, the team identified Oligohymenophorea sp. PL0344, a previously uncatalogued protist. The discovery emerged from a routine experiment led by Dr. Jamie McGowan, then a postdoctoral scientist at the Earlham Institute, and a team from the University of Oxford.
Upon assembling the organism’s genome, the researchers found that it does not follow the standard rules of genetic translation. In most life forms, DNA instructions are transcribed into messenger RNA, which ribosomes then read in three-letter sequences called codons. While most codons specify amino acids to build proteins, stop codons tell the cell when to cease production. In this organism, however, two of these stop signals, TAA and TAG, have been reassigned to code for distinct amino acids.
Protist Defies Standard Rules of Genetic Translation
By demonstrating that TAA and TAG could be independently reassigned to different building blocks, this discovery provides evidence of greater flexibility in biological systems than previously documented. Scientists generally assumed that these two specific stop signals evolved in tandem, meaning if they changed function, they would typically specify the same amino acid.
“We’re not aware of any other case where these stop codons are linked to two different amino acids. It breaks some of the rules we thought we knew about gene translation — these two codons were thought to be coupled.”
Dr. Jamie McGowan, postdoctoral scientist at the Earlham Institute
The findings were published in PLOS Genetics in October 2023.
Researchers Identify Further Ciliate Lineage Variations
The initial discovery in PL0344 prompted further investigation into other microorganisms. In December 2024, Dr. McGowan and colleagues published additional findings in PLOS Genetics, identifying independent genetic code variations in several other ciliate lineages. Analysis of genomic data, including samples from the TARA Oceans project, revealed that three previously uncultivated ciliate species use UAG to specify leucine rather than as a stop signal.
In March 2026, a study published in Microbial Genomics by researchers from the Earlham Institute and the University of Oxford investigated Bodo, a group of protists found in freshwater, brackish water, and soil.
“Scientists attempt to engineer new genetic codes — but they are also out there in nature. There are fascinating things we can find, if we look for them.”
Dr. Jamie McGowan, postdoctoral scientist at the Earlham Institute
In March 2026, a study published in Microbial Genomics by researchers from the Earlham Institute and the University of Oxford investigated Bodo, a group of protists found in freshwater, brackish water, and soil.