Arsenic Metabolism in Terrestrial Oligochaeta and Marine Polychaeta

Arsenic is probably best known for the toxic properties of some of its compounds. However the bioavailability and toxicity of arsenic is highly dependent on its chemical form varying from highly toxic inorganic to less toxic or harmless organoarsenic forms. Organoarsenic compounds are common in marine organisms where they are thought to represent metabolic end products of a process for detoxifying inorganic arsenic. In contrast to its fearing reputation, essentiality of arsenic has also been discussed, but not confirmed. Arsenosugars representing important compounds in the process of detoxification predominate in marine algae and animals feeding on them, they have also been identified in terrestrial oligochaetes and marine polychaetes by the applicant. The pathway of remarkably toxic arsenate to harmless arsenosugars in living organisms is of toxicological importance and calls for further investigation especially with respect to elucidate the origin of such compounds. The existence of arsenic in a diverse array of forms in biota gave rise to speculations about arsenic cycling and biotransformation. The most likely pathway has been proposed by Edmonds and Francesconi in 1987 suggesting a detoxification process from arsenate to arsnosugars. However, the complete biotransformation could never be confirmed. The preliminary results collected during the post doc of the applicant support strongly this proposed pathway, but need further evidence. Therefor the proposed project has the aim to clarify these transformations and to investigate the role of arsenic for organisms considering the following topics: - Confirmation of a hypothetical arsenic biotransformation pathway by verification of an arsenic containing nucleoside in Fucus serratus - Arsenolipids in biota - Toxicity of arsenic vs. possible essentiality