DNA Of Ancient Microorganisms Provide Clues On Origins Of Life
March 8, 2013

Earth’s Oldest Microorganisms Offer Insight Into Origins Of Life

April Flowers for redOrbit.com - Your Universe Online

Important genetic clues about the history of a group of ancient microorganisms called archaea and the origins of life itself have been discovered by a team of researchers. Results of this first-of-its-kind study shed light on one of Earth's oldest life forms.

"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," explained William Whitman, professor of microbiology professor at the University of Georgia´s Franklin College of Arts and Sciences.

The findings of the study were published in the early online edition of Proceedings of the National Academy of Sciences.

Along with his colleagues Felipe Sarmiento, a doctoral student in the microbiology department, and Jan Mrázek, an associate professor in the department of microbiology and the UGA Institute of Bioinformatics, Whitman surveyed 1,779 genes found in the genome of the spherical bacteria Methanococcus maripaludis to determine whether the genes were essential or not and to learn more about their functions. M. maripaludis is an aquatic member of archaea commonly found in sea marshes. The team found that 526 of the organism´s genes — roughly 30 percent — were essential to its survival, thus revealing which genes are driving the single-celled organism´s most important functions.

Archaea are relatively simple microorganisms. However, the genetic structures they use to build cellular life are similar to those found in the more complicated eukaryotic cells of complex organisms, including animals and plants. This has led scientists to theorize that eukaryotes evolved from ancient Archaea.

"DNA by itself is a rock," Whitman said. "You need all these other systems to make the DNA become a living cell."

DNA synthesis has long been thought to be one of the most conserved bioprocesses across living organisms because it is so fundamental to every existing form of life.

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

Some of the other essential genes identified are necessary for methane production, or methanogenesis, which is how these microorganisms make energy for life.

"Humans burn glucose and reduce oxygen to water, these guys burn hydrogen gas and reduce CO2 to methane," Whitman explained.

Six vitamins not commonly found in other organisms are required for methanogenesis. Understanding the production of these vitamins and their involvement in the process of changing carbon dioxide to methane sheds light on developing new and better processes for methane production for fuel.

"This was a general investigation, but there are many questions it can answer, like possibly making methane better or more efficiently," Whitman said.

Many other important findings resulted from this study.

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

"We are starting to get some insights about how this organism was actually formed," Sarmiento said. "There is a lot of information and it is interesting because it gives insights into a complete domain of life."