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Pulsed nitrogen supply induces dynamic changes in the amino acid compositionand microcystin production of the harmful cyanobacterium Planktothrix agardhii

Van de Waal, D.B. and Ferreruela, G. and Tonk, L. and Van Donk, E. and Huisman, J. and Visser, P.M. and Matthijs, H.C.P. (2010) Pulsed nitrogen supply induces dynamic changes in the amino acid compositionand microcystin production of the harmful cyanobacterium Planktothrix agardhii. FEMS Microbiology Ecology, 74, 430-438. ISSN 0168-6496.

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Official URL: http://dx.doi.org/10.1111/j.1574-6941.2010.00958.x

Abstract

Planktothrix agardhii is a widespread harmful cyanobacterium of eutrophic waters, and can produce the hepatotoxins [Asp3]microcystin-LR and [Asp3]microcystin-RR. These two microcystin variants differ in their first variable amino acid position, which is occupied by either leucine (L) or arginine (R). Although microcystins are extensively investigated, little is known about the mechanisms that determine the production of different microcystin variants. We hypothesize that enhanced nitrogen availability will increase the intracellular content of the nitrogen-rich amino acid arginine, and thereby promote the production of the variant [Asp3]microcystin-RR. To test this hypothesis, we transferred P. agardhii strain 126/3 from nitrogen-replete to nitrogen-deficient conditions, and after 2 weeks of growth under nitrogen deficiency, we added a nitrogen pulse. We found a rapid increase in the cellular nitrogen to carbon ratio and the amino acids aspartic acid and arginine, indicative of cyanophycin synthesis. This was followed by a more gradual increase of the total amino acid content connected to balanced growth. As expected, the [Asp3]microcystin-RR variant increased strongly after the nitrogen pulse, while the [Asp3]microcystin-LR increased to a much lesser extent. We conclude that sudden nitrogen enrichment affects the amino acid composition of harmful cyanobacteria, which, in turn, affects the production and composition of their microcystins.

Item Type:Article
Institutes:Nederlands Instituut voor Ecologie (NIOO)
ID Code:9112
Deposited On:04 Jan 2011 01:00
Last Modified:31 Mar 2014 10:34

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