Do algae use arsenic in membrane lipids?

Arsenic, a famous poison, has also been ascribed beneficial properties when administered in small doses. This has led to the presumption that arsenic might be useful, or even essential, to organisms at trace levels. Results from two recent independent lines of research have suggested experiments to test this hypothesis. The first, performed by scientists at the Woods Hole Oceanographic Institute, showed that, in oceanic waters with low phosphate levels, algae use nitrogen and sulfur in place of phosphorus for membrane lipid synthesis as a way of conserving their essential phosphorus reserves. The second study, performed by our group in Graz, identified a novel group of arsenic-containing lipids (arsenolipids) from marine samples. We propose to test the hypothesis that in phosphate-limiting waters, algae can utilise arsenic, ever present in seawater as arsenate, to biosynthesise arsenolipids for use in membranes. The study will be undertaken in collaboration with the Woods Hole oceanographic group and an Australian research group which will perform complementary laboratory experiments with axenic algal cultures exposed to arsenic at varying arsenate/phosphate ratios. If the hypothesis is correct, the study will provide the first evidence of arsenic serving a valuable biological role under common environmental conditions, and open a new area of arsenic biological chemistry.