Die SekundärmetaboliteDMSP und Toxinein Dinophyceae der Gattungen Prorocentrum Ehrenberg und Alexandrium Halim

A common feature among Dinophyceae is the presence of intracellular secondary metabolites. The exact function and relevance of most of these secondary compounds for its host and the interplay between different secondary metabolites is not well understood. A better characterized secondary metabolite is the tertiary sulfonium compound dimethylsulfoniopropionate (DMSP) which - as compatible solute - is for example involved in the process of osmoregulation. In some species of dinoflagellates toxins are another large class of secondary metabolites that are structurally far more complex than DMSP.The main interest of this work was focused on the existence of competition among secondary metabolites like DMSP and toxins in the metabolism of dinoflagellates. In Alexandrium minutum the synthesis of DMSP and paralytic shellfish poisoning (PSP)- toxins are induced by light and were highest in the phase of exponential growth. For that a competition for energy to reduce sulfate (for DMSP-synthesis) and nitrate (for PSP-toxinsynthesis) might occur. The investigation of different stress situations on A. minutum and A. lusitanicum shows that nitrate limitation was of no effect on the cellular accumulation of DMSP and PSP-toxins. On the other side the intracellular DMSP concentration shows a positive correlation with changing salinities, because of its function as compatible solute in osmoregulation. The contrary negative correlation between salinity and the content of PSP-toxins may be explained by the competition with DMSP which is primarily synthesized under hyperosmotic situations.