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Journal of Toxicology
Volume 2009, Article ID 954291, 8 pages
Research Article

Characteristics of a Microcystin-Degrading Bacterium under Alkaline Environmental Conditions

1Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan
2Graduate School of Bioresource Science, Akita Prefectural University, 241-438 Kaidobata-Nishi, Nakano Shimoshinjo, Akita 010-0195, Japan
3Mitsubishi Chemical Analytech Co. Ltd., 8-5-1 Tyuuou, Ami, Inashikigun, Ibaraki 300-0332, Japan
4Faculty of Engineering, The University of Tokushima, 2-1 Minamijosanjima-cho, Tokushima, Tokushima 770-8506, Japan
5School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney NSW 2052, Australia

Received 23 September 2009; Accepted 1 December 2009

Academic Editor: Michael Cunningham

Copyright © 2009 Kunihiro Okano et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The pH of the water associated with toxic blooms of cyanobacteria is typically in the alkaline range; however, previously only microcystin-degrading bacteria growing in neutral pH conditions have been isolated. Therefore, we sought to isolate and characterize an alkali-tolerant microcystin-degrading bacterium from a water bloom using microcystin-LR. Analysis of the 16S rRNA gene sequence revealed that the isolated bacterium belonged to the genus Sphingopyxis, and the strain was named C-1. Sphingopyxis sp. C-1 can grow; at pH 11.0; however, the optimum pH for growth was pH 7.0. The microcystin degradation activity of the bacterium was the greatest between pH 6.52 and pH 8.45 but was also detected at pH 10.0. The mlrA homolog encoding the microcystin-degrading enzyme in the C-1 strain was conserved. We concluded that alkali-tolerant microcystin-degrading bacterium played a key role in triggering the rapid degradation of microcystin, leading to the disappearance of toxic water blooms in aquatic environments.