Universität zu Köln

Schwarzenberger, Anke, Sadler, Thomas ORCID: 0000-0002-8621-379X and Von Elert, Eric (2013). Effect of nutrient limitation of cyanobacteria on protease inhibitor production and fitness of Daphnia magna. J. Exp. Biol., 216 (19). S. 3649 - 3656. CAMBRIDGE: COMPANY OF BIOLOGISTS LTD. ISSN 1477-9145

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Abstract

Herbivore-plant interactions have been well studied in both terrestrial and aquatic ecosystems as they are crucial for the trophic transfer of energy and matter. In nutrient-rich freshwater ecosystems, the interaction between primary producers and herbivores is to a large extent represented by Daphnia and cyanobacteria. The occurrence of cyanobacterial blooms in lakes and ponds has, at least partly, been attributed to cyanotoxins, which negatively affect the major grazer of planktonic cyanobacteria, i.e. Daphnia. Among these cyanotoxins are the widespread protease inhibitors. These inhibitors have been shown (both in vitro and in situ) to inhibit the most important group of digestive proteases in the gut of Daphnia, i.e. trypsins and chymotrypsins, and to reduce Daphnia growth. In this study we grew cultures of the cyanobacterium Microcystis sp. strain BM25 on nutrient-replete, N-depleted or P-depleted medium. We identified three different micropeptins to be the cause for the inhibitory activity of BM25 against chymotrypsins. The micropeptin content depended on nutrient availability: whereas N limitation led to a lower concentration of micropeptins per biomass, P limitation resulted in a higher production of these chymotrypsin inhibitors. The altered micropeptin content of BM25 was accompanied by changed effects on the fitness of Daphnia magna: a higher content of micropeptins led to lower IC50 values for D. magna gut proteases and vice versa. Following expectations, the lower micropeptin content in the N-depleted BM25 caused higher somatic growth of D. magna. Therefore, protease inhibitors can be regarded as a nutrient-dependent defence against grazers. Interestingly, although the P limitation of the cyanobacterium led to a higher micropeptin content, high growth of D. magna was observed when they were fed with P-depleted BM25. This might be due to reduced digestibility of P-depleted cells with putatively thick mucilaginous sheaths. These findings indicate that both the grazer and the cyanobacterium benefit from P reduction in terms of digestibility and growth inhibition, which is an interesting starting point for further studies.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Schwarzenberger, Anke UNSPECIFIED UNSPECIFIED UNSPECIFIED Sadler, Thomas UNSPECIFIED orcid.org/0000-0002-8621-379X UNSPECIFIED Von Elert, Eric UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-475207
DOI:	10.1242/jeb.088849
Journal or Publication Title:	J. Exp. Biol.
Volume:	216
Number:	19
Page Range:	S. 3649 - 3656
Date:	2013
Publisher:	COMPANY OF BIOLOGISTS LTD
Place of Publication:	CAMBRIDGE
ISSN:	1477-9145
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language BLUE-GREEN-ALGAE; MICROCYSTIS-AERUGINOSA; NUTRITIONAL CONSTRAINTS; PHOSPHORUS LIMITATION; CHEMICAL-COMPOSITION; SEASONAL SUCCESSION; GENE-EXPRESSION; FOOD QUALITY; FATTY-ACIDS; PHYTOPLANKTON Multiple languages Biology Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/47520