Complex cells likely arose from combination of bacterial and extreme-micro...( ARLINGTON Va.-- According to a new rep...)

ARLINGTON, Va.-- According to a new report, complex cells like those in the human body probably resulted from the fusion of genomes from an ancient bacterium and a simpler microbe, Archaea, best known for its ability to withstand extreme temperatures and hostile environments. The finding provides strong evidence that complex cells arose from combinations of simpler organisms in a symbiotic effort to survive.

Jim Lake and Maria Rivera, at the University of California-Los Angeles (UCLA), report their finding in the Sept. 9 issue of the journal Nature.

Scientists refer to both bacteria and Archaea as "prokaryotes"--a cell type that has no distinct nucleus to contain the genetic material, DNA, and few other specialized components. More-complex cells, known as "eukaryotes," contain a well-defined nucleus as well as compartmentalized "organelles" that carry out metabolism and transport molecules throughout the cell. Yeast cells are some of the most-primitive eukaryotes, whereas the highly specialized cells of human beings and other mammals are among the most complex.

"A major unsolved question in biology has been where eukaryotes came from, where we came from," Lake said. "The answer is that we have two parents, and we now know who those parents were."

Further, he added, the results provide a new picture of evolutionary pathways. "At least 2 billion years ago, ancestors of these two diverse prokaryotic groups fused their genomes to form the first eukaryote, and in the processes two different branches of the tree of life were fused to form the ring of life," Lake said.

The work is part of an effort supported by the National Science Foundation--the federal agency that supports research and education across all disciplines of science and engineering--to re-examine historical schemes for classifying Earth's living creatures, a process that was once based on easily observable traits. Microbes, plants or animals wer
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Contact: Leslie Fink
lfink@nsf.gov
703-292-5395
National Science Foundation
8-Sep-2004

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