The bacteria family tree may be facing some changes due to the recent work of an evolutionary biologist at Washington University in St. Louis. And that may change our understanding of when bacteria and oxygen first appeared on earth. Carrine Blank, Ph.D. , assistant professor of earth and planetary sciences in Arts & Sciences, has found that the currently accepted dates for the appearance of oxygen-producing bacteria and sulfur-producing bacteria on the early earth are not correct. She believes that these bacteria appeared on earth much later than is now believed. "It sets up a new framework of new hypotheses to be tested," she says of the new findings.

Blank's findings appear in the February 2004 issue of Geobiology.

As an evolutionary biologist, Blank said she is, "really interested in the view of the earth and microorganisms and how they come together." She uses elements of biology and geology to understand how the earth and its inhabitants co-evolved.

It is known that earth's earliest organisms were thermophilic, or able to dwell in hot environments. These organisms engaged in chemotropic metabolism -- they converted inorganic substances, such as sulfur and carbon, into energy to live. This process is similar to how we use food, water, and oxygen to generate energy.

The predecessors of modern bacteria differ in much more than age. The Archean era, which records the first billion years of Earth's geologic history, ended 2.5 billion years ago. It was at this point that the earth's biosphere must have changed and the atmospheric temperature reached 72 degrees Celsius. This is the maximum temperature at which photosynthesis can take place. Near the end of this era, about 2.7 to 2.9 billion years ago, according to Blank, stromatolites, organisms of the group Bacteria that use photosynthesis to create energy without producing oxygen, first appeared.

Blank's approach is to understand organisms by determining what materials they
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Contact: Tony Fitzpatrick
tony_fitzpatick@wustl.edu
314-935-5272
Washington University in St. Louis
13-Apr-2004

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