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Open AccessArticle

First Report of Microcystis Strains Producing MC-FR and -WR Toxins in Japan

1
Department of Food Science and Technology, National Fisheries University, 2-7-1 Nagata-honmachi, Shimonoseki, Yamaguchi 759-6595, Japan
2
National Institute of Health Sciences, 3-25-26 Tonomachi, Kawasaki, Kanagawa 210-9501, Japan
3
National Institute for Environmental Studies, Onogawa 16-2, Tsukuba, Ibaraki 305-8506, Japan
4
Okinawa Institute for the Conservation of the Environment Co. Ltd., 7-11 Suzaki, Uruma, Okinawa 904-2234, Japan
5
Faculty of Sports and Health Science, Fukuoka University, Fukuoka 814-0180, Japan
6
Tropical Technology Plus Ltd., 5-1 Suzaki, Uruma, Okinawa 904-2234, Japan
*
Author to whom correspondence should be addressed.
Toxins 2019, 11(9), 521; https://doi.org/10.3390/toxins11090521
Received: 11 August 2019 / Revised: 6 September 2019 / Accepted: 6 September 2019 / Published: 9 September 2019
(This article belongs to the Special Issue Marine Toxins Detection)
Microcystins (MCs) are a group of cyclic heptapeptide hepatotoxins produced by Microcystis and several other genera of cyanobacteria. Many structural variants have been characterized using various methods such as liquid chromatography–mass spectrometry (LC-MS) analysis, enzyme-linked immunosorbent assay (ELISA) and protein phosphatase 2A (PP2A) inhibition assay. The representative MC, MC-LR, and related cyanobacterial toxins strongly inhibit PP2A activity and can therefore be assayed by measuring the extent of PP2A inhibition. However, these methods require reference toxin standards for the quantification and identification of known MCs. To obtain various MC-producing cyanobacterial strains, we surveyed and collected MC-producing cyanobacteria from environmental sources of water in Okinawa, Japan. Using a dual assay (LC-MS analysis and PP2A inhibition assay), we identified and isolated Microcystis strains producing five MC variants (MC-LR, -RR, -LA, -FR and -WR). Approximately 4 mg of MC-WR and -FR toxins were purified from the laboratory culture of the Microcystis isolate NIES-4344. Pure MC-WR and -FR variants were prepared for future use as toxin standards in LC-MS analysis. Phylogenetic analysis based on ftsZ revealed that the NIES-4344 strain belongs to the identified groups in Microcystis aeruginosa. This is the first report of Microcystis strains producing mainly MC-WR and -FR toxins in Japan. View Full-Text
Keywords: Cyanobacteria; Microcystis; microcystins; environmental water; liquid chromatography–mass spectrometry; protein phosphatase 2A inhibition assay Cyanobacteria; Microcystis; microcystins; environmental water; liquid chromatography–mass spectrometry; protein phosphatase 2A inhibition assay
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Ikehara, T.; Kuniyoshi, K.; Yamaguchi, H.; Tanabe, Y.; Sano, T.; Yoshimoto, M.; Oshiro, N.; Nakashima, S.; Yasumoto-Hirose, M. First Report of Microcystis Strains Producing MC-FR and -WR Toxins in Japan. Toxins 2019, 11, 521.

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