Researchers Sequence and Analyze the DNA of an Ancient Parasite

An analysis of the smallest microbial genome ever sequenced supports theories that life may have originated in a hot and fiery primeval earth, according to Yale researchers and collaborators.

N. equitans defines a new kingdom, Nanoarchaeota in the domain of Archaea, in the tree of life. All life is included in the three domains Archaea, Eukaryota and Eubacteria. Archaea includes hyperthermophiles that inhabitant some of the most inhospitable environments on Earth. Scientists discovered the new organism in a hydrothermal vent of the ocean, north of Iceland. In the vent, water reaches the boiling point and beyond.

The microbe, Nanoarchaeum equitans, also provides insights into the simplest set of genes required by an organism for survival, according to the report published in the October 13 issue of the Proceedings of the National Academy of Sciences.

The tiny genome of this ancient microbe lacks genes for most metabolic functions, and lives as a parasite of Ignicoccus, a larger archaeal organism.

“The microbe must receive many essential components from Ignicoccus, since the genetic machinery for synthesis of all structural components of an organism are missing,” said Dieter Soll, professor of molecular biophysics and biochemistry and chemistry at Yale. “There are no genes for lipid, nucleotide, and amino acid biosynthesis.”

Soll said the microbial organism attracted his interest because it has about one dozen split genes. The purpose of this study was to show that two separate pieces of a gene can make individual proteins that are only functional when the pieces are acting together.

In addition to Soll, the corresponding authors include Karl Stetter of the University of Regensburg, Germany, and Michiel Noordewier of Diversa Corporation, San Diego, California.

Citation: Proceedings of the National Academy of Sciences, Vol. 100: pp 12984-12988 (October 13, 2003)

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