( A geologist from Washington University ...)Map of life on Earth could be used on Mars

A geologist from Washington University in St. Louis is developing new techniques to render a more coherent story of how primitive life arose and diverged on Earth ?with implications for Mars. Carrine Blank Ph.D., Washington University assistant professor of earth and planetary sciences in Arts & Sciences, has some insight concerning terrestrial microbes that could lead to provocative conclusions about the nature of life on Mars and other planets.

Blank approaches the task by resolving phylogenetic trees. These trees, based upon genetic sequencing data, trace the genetic relationships between what we think of as primitive organisms through trait development. The relationships between early forms of life can illuminate the relationships between organisms present on Earth today ?which fossil evidence and a method called isotopic fractionation have failed to show conclusively.

Blank most recently presented her research at the 2004 annual meeting of the Geological Society of America. Microorganisms can be divided into haves and have-nots: cells of eukaryotes contain a nucleus, while prokaryotic organisms cells do not. Prokaryotic organisms encompass archeal and bacterial domains of life. Archeal organisms diverge further into euryarcheota and Crenarcheota lineages. By piecing together genetic sequences of the three types of prokaryotic organisms, Blank creates a genetic flow chart, which can be interpreted to trace the appearance of environmental adaptations across billions of years of evolution.

Genes are inherited from parents, but can transfer from one organism to another without reproducing by a process called lateral gene transfer. Modular metabolic genes, which are not critical for cell production, account for most lateral gene transfers between microbes.

"There is a lot we're beginning to understand in terms of bacterial evolution that is still not quite clear, " Blank said. "What we're trying to resolve is the evolutionary histo
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Source:Washington University in St. Louis

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