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Applied and Environmental Microbiology, July 2006, p. 4907-4916, Vol. 72, No. 7
0099-2240/06/$08.00+0     doi:10.1128/AEM.00228-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Okadaic Acid, an Apoptogenic Toxin for Symbiotic/Parasitic Annelids in the Demosponge Suberites domuncula

Heinz C. Schröder,¹ Hans J. Breter,¹ Ernesto Fattorusso,² Hiroshi Ushijima,³ Matthias Wiens,¹ Renate Steffen,¹ Renato Batel,⁴ and Werner E. G. Müller^1*

Institut für Physiologische Chemie, Abteilung Angewandte Molekularbiologie, Universität, Duesbergweg 6, D-55099 Mainz, Germany,¹ Dipartimento di Chimica delle Sostanze Naturali, Università di Napoli Federico II, via D. Montesano 49, I-80131 Napoli, Italy,² Department of Developmental Medical Sciences, Institute of International Health, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan,³ Center for Marine Research, Institute Ruder Bokovi, HR-52210 Rovinj, Croatia⁴

Received 29 January 2006/ Accepted 8 May 2006

The role of okadaic acid (OA) in the defense system of the marine demosponge Suberites domuncula against symbiotic/parasitic annelids was examined. Bacteria within the mesohyl produced okadaic acid at concentrations between 32 ng/g and 58 ng/g of tissue (wet weight). By immunocytochemical methods and by use of antibodies against OA, we showed that the toxin was intracellularly stored in vesicles. Western blotting experiments demonstrated that OA also existed bound to a protein with a molecular weight of 35,000 which was tentatively identified as a galectin (by application of antigalectin antibodies). Annelids that are found in S. domuncula undergo apoptotic cell death. OA is one candidate inducer molecule of this process, since this toxin accumulated in these symbionts/parasites. Furthermore, we identified the cDNA encoding the multifunctional prosurvival molecule BAG-1 in S. domuncula; it undergoes strong expression in the presence of the annelid. Our data suggest that sponges use toxins (here, OA) produced from bacteria to eliminate metazoan symbionts/parasites by apoptosis.

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* Corresponding author. Mailing address: Institut für Physiologische Chemie, Abteilung Angewandte Molekularbiologie, Universität, Duesbergweg 6, 55099 Mainz, Germany. Phone: 6131 3925910. Fax: 6131 3925243. E-mail: wmueller{at}uni-mainz.de.

This article is dedicated to R. A. Lewin (Scripps Institution of Oceanography, La Jolla, CA), who 30 years ago discovered Prochloron, an algal species that stimulated our present-day view on endosymbiosis between blue-green algae and tunicates/sponges.

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Applied and Environmental Microbiology, July 2006, p. 4907-4916, Vol. 72, No. 7
0099-2240/06/$08.00+0     doi:10.1128/AEM.00228-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

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