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Journal of Bacteriology, November 2005, p. 7390-7396, Vol. 187, No. 21
0021-9193/05/$08.00+0     doi:10.1128/JB.187.21.7390-7396.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Expression Dynamics of Arsenic Respiration and Detoxification in Shewanella sp. Strain ANA-3

Chad W. Saltikov,^* Richard A. Wildman Jr., and Dianne K. Newman

California Institute of Technology, Department of Geological and Planetary Sciences, Mailstop 100-23, Pasadena, California 91125

Received 21 April 2005/ Accepted 8 August 2005

Because arsenate [As(V)] reduction by bacteria can significantly enhance arsenic mobility in the environment, it is important to be able to predict when this activity will occur. Currently, two bacterial systems are known that specifically reduce As(V), namely, a respiratory system (encoded by the arr genes) and a detoxification system (encoded by the ars genes). Here we analyze the conditions under which these two systems are expressed in Shewanella sp. strain ANA-3. The ars system is expressed under both aerobic and anaerobic conditions, whereas the arr system is only expressed anaerobically and is repressed by oxygen and nitrate. When cells are grown on As(V), the arr system is maximally induced during exponential growth, with peak expression of the ars system occurring at the beginning of stationary phase. Both the arr and ars systems are specifically induced by arsenite [As(III)], but the arr system is activated by a concentration of As(III) that is 1,000 times lower than that required for the arsC system (100 nM versus 100 µM, respectively). A double mutant was constructed that does not reduce As(V) under any growth conditions. In this strain background, As(V) is capable of inducing the arr system at low micromolar concentrations, but it does not induce the ars system. Collectively, these results demonstrate that the two As(V) reductase systems in ANA-3 respond to different amounts and types of inorganic arsenic.

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* Corresponding author. Present address: University of California, Santa Cruz, Dept. of Environmental Toxicology, Santa Cruz, CA 95064. Phone: (831) 459-5520. Fax: (831) 459-3524. E-mail: saltikov{at}etox.ucsc.edu.

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Journal of Bacteriology, November 2005, p. 7390-7396, Vol. 187, No. 21
0021-9193/05/$08.00+0     doi:10.1128/JB.187.21.7390-7396.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

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• Malasarn, D., Keeffe, J. R., Newman, D. K. (2008). Characterization of the Arsenate Respiratory Reductase from Shewanella sp. Strain ANA-3. J. Bacteriol. 190: 135-142 [Abstract] [Full Text]  
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