Light cast on origins of life

Posted by Kate Taylor

University of Georgia researchers say they've discovered important genetic clues about archaea, one of Earth's oldest life forms.

Although archaea are relatively simple organisms, the genetic systems they use to build cellular life are similar to those of more complex organisms, including animals and plants. For this reason, many scientists believe that eukaryotes - including us - evolved from ancient archaea.

"Archaea are an ancient form of microorganisms, so everything we can learn about them could help us to answer questions about the origin of life," says William Whitman, a microbiology professor in the Franklin College of Arts and Sciences.

The team surveyed 1,779 genes found in the genome of Methanococcus maripaludis, aquatic archaea commonly found in sea marshes, to determine if they were essential or not and learn more about their functions. And, they found, roughly 30 percent, or 526 genes, were essential.

These genetic systems are what allow information coded on DNA to build life.Because DNA is so fundamental to the modern cell, DNA synthesis has long been thought to be one of the most conserved processes in living organisms.

"It was a surprise when this study found that the system for making DNA was unique to the archaea," says Whitman. "Learning that it can change in the archaea suggest that ability to make DNA formed late in the evolution of life. Possibly, there may be unrecognized differences in DNA biosynthesis the eukaryotes or bacteria as well."

Other essential genes are necessary for methane production - the way these microorganisms make energy for life. "Humans burn glucose and reduce oxygen to water, these guys burn hydrogen gas and reduce CO2 to methane," says Whitman.

And the study yielded many other important results.

"We found 121 proteins that are essential for this organism that we know nothing about," says lead author Felipe Sarmiento. "This finding asks questions about their functions and the specific roles that they are playing."