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Applied and Environmental Microbiology, September 2007, p. 5725-5730, Vol. 73, No. 18
0099-2240/07/$08.00+0     doi:10.1128/AEM.00241-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Dissimilatory Iodate Reduction by Marine Pseudomonas sp. Strain SCT

Department of Bioresources Chemistry, Chiba University, 648 Matsudo, Matsudo-shi, Chiba 271-8510,¹ Department of Chemistry, Gakushuin University, Mejiro 1-5-1, Toshima-ku, Tokyo 171-8588, Japan²

Received 31 January 2007/ Accepted 12 July 2007

Bacterial iodate (IO₃^–) reduction is poorly understood largely due to the limited number of available isolates as well as the paucity of information about key enzymes involved in the reaction. In this study, an iodate-reducing bacterium, designated strain SCT, was newly isolated from marine sediment slurry. SCT is phylogenetically closely related to the denitrifying bacterium Pseudomonas stutzeri and reduced 200 µM iodate to iodide (I^–) within 12 h in an anaerobic culture containing 10 mM nitrate. The strain did not reduce iodate under the aerobic conditions. An anaerobic washed cell suspension of SCT reduced iodate when the cells were pregrown anaerobically with 10 mM nitrate and 200 µM iodate. However, cells pregrown without iodate did not reduce it. The cells in the former category showed methyl viologen-dependent iodate reductase activity (0.31 U mg^–1), which was located predominantly in the periplasmic space. Furthermore, SCT was capable of anaerobic growth with 3 mM iodate as the sole electron acceptor, and the cells showed enhanced activity with respect to iodate reductase (2.46 U mg^–1). These results suggest that SCT is a dissimilatory iodate-reducing bacterium and that its iodate reductase is induced by iodate under anaerobic growth conditions.

Published ahead of print on 20 July 2007.