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The Indirect Effect of UV: Some Good News for Microbes?Ultraviolet (UV) radiation is of great concern because its biological effects are predominantly harmful. UV damage may be direct or indirect, the latter mediated through the photochemical production of reactive oxygen species such as hydrogen peroxide. We measured the effect of H2O2 on various microbes both in the lab and in nature. At our study site in Yellowstone National Park, there is a UV-induced diurnal fluctuation of H2O2 extending up to one micron. Levels of DNA synthesis resulting from exposure to H2O2 were measured in several algal mats. Within naturally-occurring concentrations of H2O2, DNA synthesis increased. Laboratory studies showed that similar concentrations of H2O2 induce mitosis. We hypothesize that the low levels of H2O2 encountered in nature are inducing mitotic division. At higher levels of H2O2 a second peak in DNA synthesis was found which we interpret to represent DNA damage repair. These experiments suggest that in nature, the low levels of H2O2 produced may have a mitogenic rather than damaging effect. Assuming early levels of UV radiation were substantially higher at the time protists evolved, differential mitogenic effects could have influenced protistan evolution. With H2O2 likely to be present on such bodies as Mars and Europa, the response of organisms will be concentration-dependent and not linear.
Document ID
20020073064
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Rothschild, Lynn J.
(NASA Ames Research Center Moffett Field, CA United States)
Purcell, Diane
(Search for Extraterrestrial Intelligence Inst. United States)
Rogoff, Dana
(Search for Extraterrestrial Intelligence Inst. United States)
Wilson, Cindy
(Montana Univ. United States)
Brass, James A.
Date Acquired
August 20, 2013
Publication Date
January 1, 2002
Subject Category
Life Sciences (General)
Meeting Information
Meeting: Annual Meeting for the International Society for Evolutionary Protistology
Location: Vancouver, British Columbia
Country: Canada
Start Date: June 19, 2002
End Date: June 24, 2002
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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