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May 8, 2002
Life at the Extremes - Molecular Technology Uncovers Astonishing Diversity in Spain's "River of Fire"

WOODS HOLE, MA - Living conditions are tough for bacteria, algae, and other microscopic organisms in the Rio Tinto, the highly acidic, vividly crimson river that flows through the countryside of southwestern Spain. Mined since 3000 B.C., the Rio Tinto contains heavy metal concentrations that are several orders of magnitude higher than those of typical fresh water. New findings from the Rio Tinto, to be presented this week in the journal Nature, present the
first molecular description of eukaryotes in a highly acidic, high metal environment and reveal the River's incredible eukaryotic diversity. The results show that adaptation to extreme conditions is much more widespread than originally expected and provide a new understanding of the range of organisms capable of living at life's extremes and perhaps on other planets.

Eukaryota describes those organisms whose genetic material is contained within a membrane-bound nucleus. This includes plants, animals, and humans. Previous studies of the Rio Tinto relied on morphology to describe the River's diversity and alerted scientists to only a few of the evolutionary similarities between its eukaryotic organisms. By examining the DNA of organisms extracted from the Rio Tinto's sediment and biofilm, the slimy substance that coats the
surface of the River's water and rocks, scientists have uncovered new eukaryotic lineages that escaped detection by traditional methods. The work, led by Mitchell Sogin and Linda Amaral Zettler of the Marine Biological Laboratory's Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, has also revealed completely new eukaryotes as well as others which have never been seen before in such a highly-acidic environment.

In mapping out the evolutionary family tree (or phylogeny) for the Rio Tinto, Sogin, Amaral Zettler and their colleagues have detected a close relationship between the River's acid-loving eukaryotes and other species that prefer neutral environments. The short evolutionary distance between the two tells the scientists that adaptations are, in addition to being widespread, occurring rapidly when measured on an evolutionary time scale.

In addition to Amaral Zettler and Sogin, project scientists Felipe Gómez of Spain's Centro de Astrobiología, Erik Zettler of the Sea Education Association and Spain's Centro de Biología Molecular, Brendan G. Keenan of the University of Connecticut, Storrs, and Ricardo Amils of the Centro de Astrobiología, and the Centro de Biología Molecular. The project was funded by the NSF's Life in Extreme Environments (or LexEn) Program and NASA's Astrobiology Institute.

The Marine Biological Laboratory is an independent scientific institution, founded in 1888, that undertakes the highest level of creative research and education in biology, including the biomedical and environmental sciences. The Josephine Bay Paul Center in Comparative Molecular Biology and Evolution was created in 1997. The major emphasis of the Center is placed upon comparative/phylognetic studies of genes and genomes, molecular microbial ecology/biodiversity and evolution of host defense mechanisms in marine invertebrates. Through studies of genotypic diversity across all phyla and the use of modern molecular genetics and phylogeny, the Center hopes to gain insights into the evolution of molecular structure and function.