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Mar. Drugs 2009, 7(4), 497-522; doi:10.3390/md7040497

Preliminary Characterization of Extracellular Allelochemicals of the Toxic Marine Dinoflagellate Alexandrium tamarense Using a Rhodomonas salina Bioassay

Alfred Wegener Institute for Polar and Maine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany
Author to whom correspondence should be addressed.
Received: 18 September 2009 / Revised: 28 October 2009 / Accepted: 29 October 2009 / Published: 2 November 2009
(This article belongs to the Special Issue Bioactive Compounds from Marine Microbes)
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Members of the marine dinoflagellate genus Alexandrium are known to exude allelochemicals, unrelated to well-known neurotoxins (PSP-toxins, spirolides), with negative effects on other phytoplankton and marine grazers. Physico/chemical characterization of extracellular lytic compounds of A. tamarense, quantified by Rhodomonas salina bioassay, showed that the lytic activity, and hence presumably the compounds were stable over wide ranges of temperatures and pH and were refractory to bacterial degradation. Two distinct lytic fractions were collected by reversed-phase solid-phase extraction. The more hydrophilic fraction accounted for about 2% of the whole lytic activity of the A. tamarense culture supernatant, while the less hydrophilic one accounted for about 98% of activity. Although temporal stability of the compounds is high, substantial losses were evident during purification. Lytic activity was best removed from aqueous phase with chloroform-methanol (3:1). A “pseudo-loss” of lytic activity in undisturbed and low-concentrated samples and high activity of an emulsion between aqueous and n-hexane phase after liquid-liquid partition are strong evidence for the presence of amphipathic compounds. Lytic activity in the early fraction of gel permeation chromatography and lack of activity after 5 kD ultrafiltration indicate that the lytic agents form large aggregates or macromolecular complexes. View Full-Text
Keywords: Alexandrium tamarense; allelochemicals; cell lysis; extracellular compound Alexandrium tamarense; allelochemicals; cell lysis; extracellular compound

This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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Ma, H.; Krock, B.; Tillmann, U.; Cembella, A. Preliminary Characterization of Extracellular Allelochemicals of the Toxic Marine Dinoflagellate Alexandrium tamarense Using a Rhodomonas salina Bioassay. Mar. Drugs 2009, 7, 497-522.

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