Nitrogen is crucial for each known type of life on Earth. Now, scientists say this common element might also help explain how youth evolved on our planet and the way life might need developed elsewhere within the universe.
“All living things need nitrogen to survive and even though it’s all around us, we don’t have direct access to it,” says biochemist Lance Seefeld of Utah State University. “Enzymes called nitrogenases enable nitrogen fixation, which changes nitrogen into a form that plants, animals, humans and other organisms can access. And we’re just beginning to understand how much this nitrogen has evolved over Earth’s four billion-year history.”
In a study published in , Seefeldt, USU senior scientist Derek Harris, and colleagues from the NASA-funded Metal Utilization and Selection across Eons (MUSE) project on the University of Wisconsin-Madison used synthetic biology to work backwards from modern nitrogenases and reconstruct possible versions of those lineages.
Reconstructing ancient nitrogen-fixing enzymes
“Our role in the study was to characterize a library of artificially reconstructed ancestral nitrogenase genes,” says Harris. “Under controlled lab conditions, we measured nitrogen isotope fractionation in the cell biomass of the engineered strain.”
The research allowed scientists to look at how ancient nitrogenases might need worked billions of years ago.
Seefeld, who serves as professor and chair of USU’s Department of Chemistry and Biochemistry, has spent greater than 30 years studying the structure and performance of nitrogenase. The ability of those enzymes to recreate ancient forms marks a serious breakthrough in efforts to know the origins of life on Earth and possibly other worlds, he says.
“Until now, science has relied on ancient rock and fossils to study early life,” he says. “Our planet was very different billions of years ago. Modern microbes access atmospheric sources of nitrogen through nitrogenase, which is just one family of enzymes. Studies of fossilized enzymes assume that ancient enzymes developed the same isotopic signature as modern enzymes.”
New Clues About Early Earth
According to Seefeld, reconstructed nitrogenases provide a brand new option to investigate what conditions might need been like on Earth and its atmosphere within the distant past.
“Understanding both ancient and modern nitrogenases is critical to helping us address current agricultural challenges in a changing climate, including areas at risk of drought and famine due to lack of access to commercial fertilizers,” he says.
These findings could have practical applications beyond Earth. Seefeld, who has participated in other NASA-funded projects, says the work contributes to ongoing efforts to find out how food will be grown in space and on Mars.
Implications for the search for all times beyond Earth
Betül Kaçar, professor of bacteriology at UW-Madison, director of the MUSE project, and corresponding creator of the study, says the findings provide a transparent view of how life survived and evolved before oxygen-dependent organisms modified the planet.
“The search for life starts here at home, and our home is four billion years old,” she says. “So, we need to understand our past. We need to understand life before us, if we want to understand life beyond us and life elsewhere.”