Chromosome organization affects evolution of DNA in archaea

The structure of how DNA is stored in archaea makes a significant difference to how quickly it evolves, according to a new study by Indiana University researchers.

The study, led by molecular biologist Stephen Bell, Distinguished Professor and chair of the College of Arts and Sciences' Department of Molecular and Cellular Biochemistry at IU Bloomington, was recently published in Nature Microbiology. Its findings have the potential to impact research on the treatment of genetic diseases such as cancer.

The most exciting thing we revealed is the idea that the shape of a DNA molecule can affect its ability to change. In the early 20th century, modernist architecture had the idea that the form of a building should follow its function. But what we're seeing in these organisms is that over time, form is actually affecting evolution. How DNA is structured can change it, creating an evolutionary feedback loop."

Stephen Bell, Distinguished Professor and Chair of the College of Arts and Sciences' Department of Molecular and Cellular Biochemistry at IU Bloomington

Archaea, single-celled microorganisms discovered in the 1970s, are one of the three domains of life on Earth, which scientists use to classify all life forms. The other two domains are bacteria and eucaryotes, which include mammals and humans. Archaea is possibly the most ancient domain of the three.

"You can think of archaea as molecular fossils," Bell said. "Studying them is like getting in a time machine and looking back about 2 billion years."

Previous research by Bell and his IU collaborators, Rachel Samson, an assistant research scientist in the Department of Molecular and Cellular Biochemistry, and Naomichi Takemata, a postdoctoral researcher in Bell's lab, found that certain species of archaea organize their chromosomes, which store DNA, into two compartments.

For this new study, Bell lab postdoctoral researcher Catherine Badel, Samson and Bell measured mutation rates of chromosomes in 11 species in a certain genus of archaea. Their analysis demonstrated that the DNA in one compartment, where it was stored more compactly, changed at a much faster rate than the other compartment.

The discovery is important, Bell said, because understanding the form and function of DNA may help researchers better understand all life forms, including humans. That knowledge could one day help researchers improve treatments for genetic diseases or other genetic errors.

"We need to understand how something works before we can understand how to fix it when something goes wrong," he said.

This research builds on earlier work by Bell and his collaborators, who in a previous study found similarities between human and archaea chromosomes.