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Applied and Environmental Microbiology, March 2000, p. 1001-1006, Vol. 66, No. 3
Marine Biology Research Division, Scripps
Institution of Oceanography, University of California, La Jolla,
California 92093
Received 18 October 1999/Accepted 4 January 2000
Numerous agents can damage the DNA of prokaryotes in the
environment (e.g., reactive oxygen species, irradiation, and secondary metabolites such as antibiotics, enzymes, starvation, etc.). The large
number of potential DNA-damaging agents, as well as their diverse modes
of action, precludes a simple test of DNA damage based on detection of
nucleic acid breakdown products. In this study, free 3'-OH DNA ends,
produced by either direct damage or excision DNA repair, were used to
assess DNA damage. Terminal deoxyribonucleotide transferase
(TdT)-mediated dUTP nick end labeling (TUNEL) is a procedure in which
3'-OH DNA ends are enzymatically labeled with dUTP-fluorescein
isothiocyanate using TdT. Cells labeled by this method can be detected
using fluorescence microscopy or flow cytometry. TUNEL was used to
measure hydrogen peroxide-induced DNA damage in the archaeon
Haloferax volcanii and the bacterium Escherichia
coli. DNA repair systems were implicated in the hydrogen peroxide-dependent generation of 3'-OH DNA ends by the finding that the
protein synthesis inhibitors chloramphenicol and diphtheria toxin
blocked TUNEL labeling of E. coli and H. volcanii, respectively. DNA damage induced by UV light and
bacteriophage infection was also measured using TUNEL. This methodology
should be useful in applications where DNA damage and repair are of
interest, including mutant screening and monitoring of DNA damage in
the environment.
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Detection of DNA Damage in Prokaryotes by Terminal
Deoxyribonucleotide Transferase-Mediated dUTP Nick End
Labeling
*
Corresponding author. Mailing address: Marine Biology
Research Division, Hubbs Hall 4200, Scripps Institution of
Oceanography, University of California, La Jolla, CA 92037. Phone:
(858) 534-3196. Fax: (858) 534-7313. E-mail:
forest{at}ucsd.edu.
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