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Applied and Environmental Microbiology, January 2000, p. 199-205, Vol. 66, No. 1
Department of Veterinary Science and
Microbiology, University of Arizona, Tucson, Arizona 85721
Received 2 August 1999/Accepted 6 October 1999
The loss of stratospheric ozone and the accompanying increase in
solar UV flux have led to concerns regarding decreases in global
microbial productivity. Central to understanding this process is
determining the types and amounts of DNA damage in microbes caused by
solar UV irradiation. While UV irradiation of dormant Bacillus
subtilis endospores results mainly in formation of the "spore
photoproduct" 5-thyminyl-5,6-dihydrothymine, genetic evidence indicates that an additional DNA photoproduct(s) may be formed in
spores exposed to solar UV-B and UV-A radiation (Y. Xue and W. L. Nicholson, Appl. Environ. Microbiol. 62:2221-2227, 1996). We examined
the occurrence of double-strand breaks, single-strand breaks,
cyclobutane pyrimidine dimers, and apurinic-apyrimidinic sites in spore
DNA under several UV irradiation conditions by using enzymatic probes
and neutral or alkaline agarose gel electrophoresis. DNA from spores
irradiated with artificial 254-nm UV-C radiation accumulated
single-strand breaks, double-strand breaks, and cyclobutane pyrimidine
dimers, while DNA from spores exposed to artificial UV-B radiation
(wavelengths, 290 to 310 nm) accumulated only cyclobutane pyrimidine
dimers. DNA from spores exposed to full-spectrum sunlight (UV-B and
UV-A radiation) accumulated single-strand breaks, double-strand breaks,
and cyclobutane pyrimidine dimers, whereas DNA from spores exposed to
sunlight from which the UV-B component had been removed with a filter
("UV-A sunlight") accumulated only single-strand breaks and
double-strand breaks. Apurinic-apyrimidinic sites were not detected in
spore DNA under any of the irradiation conditions used. Our data
indicate that there is a complex spectrum of UV photoproducts in DNA of
bacterial spores exposed to solar UV irradiation in the environment.
0099-2240/0/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Artificial and Solar UV Radiation Induces Strand
Breaks and Cyclobutane Pyrimidine Dimers in Bacillus
subtilis Spore DNA
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Corresponding author. Mailing address: Department of
Veterinary Science and Microbiology, University of Arizona, Tucson, AZ 85721. Phone: (520) 621-2157. Fax: (520) 621-6366. E-mail:
wln{at}u.arizona.edu.
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