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β-Cyclocitral, a Grazer Defence Signal Unique to the Cyanobacterium Microcystis

Jüttner, Friedrich ; Watson, Susan ; von Elert, Eric ; Köster, Oliver

In: Journal of Chemical Ecology, 2010, vol. 36, no. 12, p. 1387-1397

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    Titre
    • β-Cyclocitral, a Grazer Defence Signal Unique to the Cyanobacterium Microcystis
    Auteur
    • Jüttner, Friedrich. University of Zürich, Limnological Station, CH-8802, Kilchberg, Switzerland
    • Watson, Susan. Aquatic Ecosystem Management Research Canada Centre for Inland Waters, Environment Canada, 867, Lakeshore Rd, Burlington, ON, Canada
    • von Elert, Eric. University of Cologne, Cologne Biocentre, Zülpicher Strasse 47b, 50674, Köln, Germany
    • Köster, Oliver. Zürich Water Supply (WVZ), Hardhof 9, P.O. Box1179, CH-8021, Zürich, Switzerland
    Type de document
    • Postprint
    Langue
    • Anglais
    Publié dans
    • Journal of Chemical Ecology, 2010, vol. 36, no. 12, p. 1387-1397. Springer-Verlag
    Autre version électronique
    Identifiant OAI-PMH
    • oai:doc.rero.ch:310584
    Summary
    β-Cyclocitral is often present in eutrophic waters and is a well known source of airborne and drinking water malodor, but its production and functional ecology are unresolved. This volatile organic compound (VOC) is derived from the catalytic breakdown of β-carotene, and evidence indicates that it is produced by the activation of a specific carotene oxygenase by all species of the bloom-forming cyanobacterium Microcystis. Previous work has shown that β-cyclocitral affects grazer behavior, but the nature of this interaction and its influence on predator-prey dynamics was unresolved. The present study combined analytical and behavioral studies to evaluate this interaction by using Microcystis NRC-1 and Daphnia magna. Results showed that β-cyclocitral was undetectable in live Microcystis cells, or present only at extremely low concentrations (2.6 amol /cell). In contrast, cell rupture activated a rapid carotene oxygenase reaction, which produced high amounts (77 ± 5.5 amol β-cyclocitral/cell), corresponding to a calculated maximum intracellular concentration of 2.2mM. The behavioral response of Daphnia magna to β-cyclocitral was evaluated in a bbe© Daphnia toximeter, where β-cyclocitral treatments induced a marked increase in swimming velocity. Acclimation took place within a few minutes, when Daphnia returned to normal swimming velocity while still exposed to β-cyclocitral. The minimum VOC concentration (odor threshold) that elicited a significant grazer response was 750nM β-cyclocitral, some 2,900 times lower than the per capita yield of a growing Microcystis cell after activation. Under natural conditions, initial grazer-related or other mode of cell rupture would lead to the development of a robust β-cyclocitral microzone around Microcystis colonies, thus acting as both a powerful repellent and signal of poor quality food to grazers