Primer on Microbial Genomics cont'd
Shaking Up the Tree of Life
[Microbe positional data provided by Frank Larimer (Oak Ridge National Laboratory)]
This tree of life--or phylogenetic tree--traces the pattern of descent of all life over millions of years into three major branches: Bacteria, Archaea, and Eucarya. Until 1996, however, scientists had confirmed the existence of only two of those branches. And although Earth's biomass is largely microbial, most previous studies focused primarily on a tiny portion at the tip of the Eucarya branch, the region containing animals and plants. Newly available microbial DNA sequences on the other two branches, many supported in the DOE Microbial Genome Program (MGP), have enabled large-scale genomic comparisons among different organisms for the first time, and the information is changing some long-held views of the history of life.
Methanococcus jannaschii
photomicrograph of M. jannaschii
In 1996, for example, comparisons of genomic sequences from the microbe Methanococcus jannaschii (electron photomicrograph above) with those of other organisms confirmed the existence of the archaeal branch of life. M. jannaschii was first isolated in 1983 in the area of a "smoker," a hydrothermal vent on the floor of the Pacific Ocean. Thriving at pressures that would crush a conventional submarine, this heat-loving, methane-producing microbes lives without sunlight, oxygen, or organic carbon. DOE MGP researchers hope to exploit these unusual properties, along with the unique characteristics of other microbes studied. Increasing knowledge about microbial life and its enormous range of capacities will have far-reaching implications for environmental, energy, health, and industrial applications.
New revelations also are showing some surprising connections among microbes previously thought to have diverged evolutionarily long ago. Researchers expect that, in addition to providing intriguing new details on phylogenetic trees, the continued explosion of genome data and analysis tools will lead to new insights into how biological systems function.
hydrothermal vent where M. jannaschii was found
[Photomicrograph of M. Jannaschii reprinted with permission from Springer-Verlag; photograph of hydrothermal vent, copyright Woods Hole Oceanographic Institution.]
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Text from Human Genome Program, U.S. Department of Energy, Microbial Genome Program Report, 2000.
