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Aquatic Microbial Ecology

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AME 39:85-95 (2005)  -  doi:10.3354/ame039085

Cell cycle dependent expression of toxicity by the ichthyotoxic prymnesiophyte Chrysochromulina polylepis

Erik Eschbach1, Uwe John2,*, Marcus Reckermann3, Allan D. Cembella2, Bente Edvardsen4, Linda K. Medlin2

1Lohmann Animal Health GmbH & Co. KG, Heinz-Lohmann-Strasse 4, 27472 Cuxhaven, Germany
2Alfred-Wegener-Institut für Polar- und Meeresforschung, Am Handelshafen 12, 27570 Bremerhaven, Germany
3Coastal Research Laboratory, Research and Technology Centre of Kiel University, Otto-Hahn-Platz 3, 24098 Kiel, Germany
4Department of Biology, University of Oslo, PO Box, 1069 Blindern, 0316 Oslo, Norway
*Corresponding author. Email:

ABSTRACT: The coupling of toxicity expression with cell-cycle phases was studied in the toxic marine prymnesiophyte Chrysochromulina polylepis Manton & Parke, Clone B1511. Cell synchronisation of cultures in exponential or early stationary growth phases under nutrient-replete conditions was achieved by manipulation of the photoperiod. Chlorophyll a (chl a) and cell number increased in a stepwise manner, but were asynchronous, with chl a increasing during the light period and cell number increasing during the dark period. In the course of the light period, nearly all cells clustered in the G1 (Gap 1) phase, which lasted for about 20 h. DNA synthesis (S phase) occurred mainly in the dark during a discrete period (about 4 h) and G2 (Gap 2) and mitosis (M) were always completed before the end of the dark period. Toxicity expression, measured by the erythrocyte lysis assay (ELA), exhibited a dramatic drop in LC50 values (increase in toxicity) during the light period, although this effect was less pronounced after the first 2 generations of cell division when the cultures had entered the stationary phase. Similarly, haemolytic activity per unit cell volume decreased by a factor of 3 to 4 during the dark period over the first 48 h, but became irregular towards the end of the experiment. In this study, the light-dependent effect on toxicity and relationship to discrete phases of the cell cycle are demonstrated for the first time in a prymnesiophyte.

KEY WORDS: Cell cycle · Ichthyotoxins · Phytoflagellates · Prymnesiophytes · Chrysochromulina polylepis

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