Researchers at the University of Nebraska-Lincoln have found evidence of epigenetic evolution in archaea. According to the authors, this is the first observation of epigenetic changes occurring in non-eukaryotic organisms. Their findings have been published in PNAS.
The researchers discovered the phenomenon while doing research in Sulfolobus solfataricus, a sulfur-eating species that thrives in the boiling, acidic springs of Yellowstone National Park. The researchers exposed the species to increasing levels of acidity over the years and were able to evolve three strains with 178 times greater resistance than their original counterparts in Yellowstone.
The team predicted the DNA of the archaea would be mutated and they could trace the mutation back to find what caused extreme resistance, but this was not the case. One of the strains evolved the resistance despite no mutations in its DNA and the other two underwent mutations in genes that do not contribute to acid resistance.
Instead, it appeared that proteins were epigenetically controlling the expression of resistance-relevant genes. When the researchers disrupted these proteins, the resistance abruptly disappeared in subsequent generations.
This finding is significant as epigenetics has thus far been hard to study in eukaryotes, the authors believe that the relative simplicity of archaea could allow researchers to investigate epigenetic questions that were previously time and cost prohibitive.
"We don't know what flips the switch in humans that changes epigenetic traits," said Paul Blum, Charles Bessey Professor of biological sciences at Nebraska. "And we sure don't know how to reverse it very often. That's the first thing we'll go after: how to turn it on, how to turn it off, how to get it to switch. And that has benefits when you think about (managing) traits in us or traits in plants."
The discovery also raises questions into how archaea and eukaryotes both have come to adopt epigenetic methods, which could have evolutionary implications. Additionally, the researchers wonder if epigenetics might explain why no known archaea cause disease or wage warfare against each other like bacteria do.