Reactive oxygen also plays an important role in human, animal and plant health, because it is often used as a host defense to inhibit the growth of unwanted microbial pathogens. In fact, it appears that even non-photosynthetic bacteria, including human and animal pathogens like Vibrio and Pseudomonads have systems to sense and protect themselves from singlet oxygen, says Donohue. Other reactive oxygen species - often called "free radicals" - are thought to be at the root of many debilitating diseases.

"There have been considerable advances in our understanding of how cells protect themselves from several reactive oxygen species," says Donohue. "However, nothing has previously been known about how cells alter gene expression to respond to singlet oxygen. We may now be able to design pharmaceuticals that target this response, and ultimately may help us mitigate disease."

Donohue's co-authors on his study were a microbiology graduate student, Jennifer Anthony, and a bacteriology undergraduate, Kristin Warczak. The project was supported by a grant from the National Institute of General Medical Sciences, the University of Wisconsin-Madison Distinguished Fellowship Program, and the University of Wisconsin-Madison Hilldale undergraduate research scholars program.

Cells that grow by photosynthesis use chlorophyll to absorb solar energy. The following NASA satellite image maps chlorophyll concentrations on land as well as in oceans, lakes and seas. This image provides a snapshot of photosynthetic capacity and significant sources of singlet oxygen, a toxic byproduct of photosynthesis, in the biosphere. See the image at: http://
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Contact: Tim Donohue
tdonohue@bact.wisc.edu
608-262-4663
University of Wisconsin-Madison
25-Apr-2005