This award will support collaborative research in biological oceanography between Dr. Edward Carpenter, State University of New York at Stony Brook, and Dr. Birgitta Bergman, Institute of Physiological Botany, University of Uppsala, Sweden. The objective of the proposed research is to study the physiology of nitrogen fixation in the pelagic cyanobacterium Trichodesmium. This organism is significant in the biology of the world's oceans as a major contributor of new nitrogen to tropical and subtropical seas. In the proposed project, Dr. Carpenter will study advanced techniques on enzyme localization, molecular biology and electron microscopy in order to address major unresolved questions concerning this enigmatic organism, in particular, how this non-heterocystous colony is able to fix nitrogen during the day under aerobic conditions. He will focus on: 1) the location and abundance of the enzyme nitrogenase through diel cycles, 2) the localization and abundance of N transforming enzymes GS and GOGAT, with the goal of understanding how fixed nitrogen is transferred from diazotrophic cells to vegetative cells, 3) the location of oxygen protective enzymes, such as uptake hydrogenases and superoxide dismutase, and 4) the location of other proteins involved in photosynthesis. The two major Trichodesmium species, erythraeum and thiebautii, will be contrasted. The research will be carried out through the study of Trichodesmium samples at the Institute of Physiological Botany in Uppsala, jointly with Dr. Bergman. The complementary expertise of the two investigators in immuno-localization at the LM and TEM level of key proteins in cynobacteria will contribute to the success of the proposed project.
