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Aquatic Microbial Ecology

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AME 24:51-59 (2001)  -  doi:10.3354/ame024051

Quantification of recA gene expression as an indicator of repair potential in marine bacterioplankton communities of Antarctica

Melissa G. Booth1,*, LeAnna Hutchinson2, Margaret Brumsted2, Peter Aas2, Richard B. Coffin3, Roswell C. Downer Jr4, Cheryl A. Kelley5, M. Maille Lyons2, J. Dean Pakulski2, Sonya L. Holder Sandvik6, Wade H. Jeffrey2, Robert V. Miller1,**

1Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, Oklahoma 74078, USA
2Center for Environmental Diagnosis and Bioremediation, University of West Florida, Pensacola, Florida 32514, USA
3Naval Research Laboratory, Washington, DC, Washington 20375, USA
4Department of Oceanography, Texas A&M University, College Station, Texas 77840, USA
5Department of Geological Sciences, University of Missouri, Columbia, Missouri 65211, USA
6National Research Council, c/o U.S. EPA, Gulf Breeze, Florida 32561, USA
*Present address: Skidaway Institute of Oceanography, Savannah, Georgia 31405, USA **Corresponding author. E-mail:

ABSTRACT: Marine bacteria in surface waters must cope daily with the damaging effects of exposure to solar radiation (containing both UV-A and UV-B wavelengths), which produces lesions in their DNA. As the stratospheric ozone layer is depleted, these coping mechanisms are likely to play an even more important role in the viability of marine bacterial communities. The recA gene is ubiquitous among eubacteria and is highly conserved both in nucleotide and amino acid sequence. Besides its role in generalized recombination, the gene¹s translational product, RecA, is the regulator of Œdark repair¹ activity (DNA-repair mechanisms that do not require visible light as a cofactor). We have taken advantage of this function and used recA gene expression as a barometer of the DNA-damage repair capacity of bacterial assemblages in the Southern Ocean. Studies were conducted in the Gerlache Strait, Antarctica, in the austral springs of 1995 and 1996. Analysis of both recA mRNA and RecA protein extracted from natural communities indicated that the level of expression of this gene varied in a diel fashion, suggesting an increased repair capacity in these organisms. These included an early morning rise in RecA levels followed by a plateau or even a reduction in RecA concentration during the remainder of the day. A much greater increase in RecA was consistently observed after sunset, followed by a constant decrease during the night. Microcosm experiments with a RecA+ Gerlache Strait γ-proteobacteria isolate, RM11001, demonstrated a similar diel pattern of expression. These studies demonstrate the usefulness of RecA as a biological indicator of DNA repair capacity in natural bacterial assemblages. They indicate that Œdark repair¹ of DNA damage is an important coping mechanism for bacteria in the marine environment of Antarctica.

KEY WORDS: Southern Ocean · Antarctica · Solar UV radiation · DNA repair · Marine bacterioplankton communities · recA gene · RecA protein

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