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High Diversity of Microcystin Chemotypes within a Summer Bloom of the Cyanobacterium Microcystis botrys
Open AccessArticle

Phosphate Limitation Increases Content of Protease Inhibitors in the Cyanobacterium Microcystis aeruginosa

1
Workgroup Aquatic Chemical Ecology, Institute for Zoology, University of Cologne, 50674 Cologne, Germany
2
Institute of Hydrobiology, Technische Universität (TU) Dresden, 01062 Dresden, Germany
*
Author to whom correspondence should be addressed.
Toxins 2020, 12(1), 33; https://doi.org/10.3390/toxins12010033 (registering DOI)
Received: 13 October 2019 / Revised: 21 December 2019 / Accepted: 1 January 2020 / Published: 6 January 2020
(This article belongs to the Special Issue Environmental Drivers of Algal and Cyanobacterial Toxin Dynamics)
Increased anthropogenic nutrient input has led to eutrophication of lakes and ponds, resulting worldwide in more frequent and severe cyanobacterial blooms. In particular, enhanced availability of phosphorus (P) can promote cyanobacterial mass developments and may affect the content of secondary metabolites in cyanobacteria, such as protease inhibitors (PIs). PIs are common among cyanobacteria and have been shown to negatively affect herbivorous zooplankton. Here, we test the hypothesis that P-limitation reduces the growth of Microcystis, but increases the content of PIs. In batch culture experiments with eight different initial phosphate concentrations (5–75 µM) we determined growth, stoichiometry, and PI content of Microcystis aeruginosa NIVA Cya 43. This strain produces the protease inhibitor BN920 that is converted by chlorination to CP954, which constitutes the major PI in this strain. C:N:P-ratios of the biomass indicated variation of P-limitation with treatment and time. When normalized to biomass, the PI content varied up to nearly nineteen-fold with treatment and time and was highest in the low-P treatments, especially during the mid-exponential growth phase. However, these effects were alleviated under nitrogen co-limitation. The content of CP954 showed an inverse u-shaped response to growth rate and C:N-ratio of the cyanobacterial biomass, whereas it increased with cyanobacterial C:P. The results indicate that P-limitation supports a higher content of defensive PIs and may indirectly foster cyanobacterial blooms by increasing the negative interference of cyanobacteria with their consumers. View Full-Text
Keywords: eutrophication; freshwater; protease inhibitors; toxin production; cyanotoxins eutrophication; freshwater; protease inhibitors; toxin production; cyanotoxins
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Burberg, C.; Petzoldt, T.; von Elert, E. Phosphate Limitation Increases Content of Protease Inhibitors in the Cyanobacterium Microcystis aeruginosa. Toxins 2020, 12, 33.

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