The award was submitted in response to solicitation NSF 08-602: International Collaboration in Chemistry between US Investigators and their Counterparts Abroad (ICC). The NSF and the partnering international funding agency co-reviewed and made a joint funding decision on this proposal. NSF will support the research of the U.S. investigators while the partnering international funding agency will support the research of the collaborating foreign investigators.
This research award by the Inorganic, Bioinorganic and Organometallic Chemistry Program and the Office of International Science and Engineering supports work by Professor Carl J. Carrano at San Diego State University who, with his German collaborator Berthold Matzanke (supported by the Deutsche Forschunsgemeinschaft), will conduct fundamental studies on the Iron Uptake and Storage Mechanisms in Marine Macroalgae. Iron is a critical micronutrient for all plant species including those associated with the marine environment. Indeed iron has been found to be the growth limiting nutrient with respect to the growth of phytoplankton in large areas of all the oceans. Thus the chemistry and biochemistry of how this element is acquired, stored and processed is of critical importance to an understanding of the marine coastal environments in which macroalgae are usually the dominant organisms in terms of biomass, often forming extensive kelp forests. The key role of kelp forests, effectively constituting an interface between the ocean, the atmosphere and land masses, impacts such diverse areas as oceanic primary productivity, alternate energy sources and global carbon sequestration. Using a variety of sophisticated chemical, molecular and biological tools this project will increase our understanding of this environmentally important class of marine organisms.
Marine macroalgae (seaweeds) represent an important resource with a wide range of uses in the food, cosmetic, and fertilizer industries with an estimated annual global value of about 4 billion dollars. They are also attracting increasing attention as a source for biofuels that do not compete with terrestrial plants for food production. This work also provides for the training of graduate (both MS and PhD) and undergraduate students in a wide range of important techniques. Because San Diego State University has a high minority population (10th largest grantor of minority bachelor's degrees in the USA) it is expected to impact minority recruitment and training in the sciences. The international nature of the research team and the proposed student exchanges will also promote international cooperation in science.
Intellectual Merit: Iron is an essential element for all living organisms due to its ubiquitous role in redox and other enzymes, especially in the context of respiration and photosynthesis. The iron uptake and storage systems of terrestrial/ higher plants are now reasonably well understood with two basic strategies for iron uptake have been distinguished. In contrast, there is far less knowledge about the corresponding systems in marine, plant-like lineages i.e. the algae. Marine algae, particularly the macro algae or seaweeds represent an important resource with a wide range of uses in the food, cosmetic, and fertilizer industries with an estimated annual global value of about 5 billion dollars They are also attracting increasing attention as a source for biofuels that do not compete with terrestrial plants for food production. The microalgae or phytoplankton are the origin of most of the primary productivity in the ocean and form the base of the entire food chain. Thus it is important to understand how such organisms acquire their needed iron the iron level in ocean waters is even lower than in most terrestrial environments. Indeed, iron availability is now well known to limit primary productivity in certain oceanic regimes leading to controversial iron fertilization global engineering approaches to mitigate increasing atmospheric carbon dioxide. During the grant period we utilized a multi-disciplinary, multi-pronged approach aimed at elucidating aspects of iron uptake and storage in important marine algae which combined bioinformatics, molecular biology, microbiology, natural products chemistry, and biochemistry with cutting-edge spectroscopic methods. The following results were obtained. Uptake Mechanisms. Similar to many land plants we find that iron uptake in the marine bloom forming green algae Tetraselmis suecica involve an initial reductive step involving a genetically encoded inducible cell surface reductase. This reduction is then followed by a reoxidation of the Fe(II) by a multi-copper oxidase and transport across the membrane as Fe(III). A reductive-oxidative pathway has also been found for the brown alga Ectocarpus siliculosus. Among the coccolithophore branch of the marine algae we find that in Emiliana huxleyii a non-reductive (direct uptake of Fe(III)) uptake path appears probable. Storage Mechanisms. The presence of a class of proteins called ferritins represent the standard means of iron storage throughout the entire tree of life although there are a few exceptions. If an organism is not employing the ferritin strategy of iron storage, all the potential functions of ferritins must be replaced by novel compounds or functional cell compartments. Using detailed temperature dependent Mössbauer and EPR measurements we have shed some light on the nature of iron stores in non-ferritin containing marine algae. Using such experiments we have identified what believe to be mineral phase storage forms of iron in the green alga Tetraselmis suecica, the brown alga, Ectocarpus siliculosus and the coccolithophore Emiliana huxleyi. Whether these mineral phases are in the form of ferritin-like proteins which lacks significant homology to previously studied systems, or is sequestered in some sort of vacuole, remains to be determined. Broader Impacts: A wide range of graduate undergraduate and postdoc’s have worked on this project resulting in one paper in over ten published papers Many of the above publications contain undergraduate and/or graduate students as coauthors and several are the product of graduate student theses. In addition SDSU students have made several trips to visit our German and UK collaborators and have spent in aggregate several months in Germany, Scotland and elsewhere in Europe on grant funded exchanges that further international cooperation in science.
