A Novel Molecular Approach to Nitrogen-Fixation in Marine Ecosystems

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Nitrogen fixation is an important component of the nitrogen cycle in the sea. Presently, it appears that the colonial cyanobacterium Trichodesmium is the major diazotroph in the euphotic zone of the open ocean. A number of other species could potentially contribute significantly to the fixation of N2, but may have escaped attention due to the difficulties of culture and the measurement of N2-fixation in situ. In this project, Dr. Zehr and collaborators will present a new approach to the detection and characterization of N2-fixing microorganisms in the marine environment. They will use a very sensitive molecular technique, the polymerase chain reaction (PCR), to identify and characterize nitrogen-fixing genes in a variety of marine environments. The use of this technique will settle a number of long-standing issues of the presence of N2-fixation potential i planktonic and benthic environments. Furthermore, the product of this research will be a DNA sequence database and cloned nif genes which can be used for detailed investigations of the ecological diversity of N2-fixing microorganisms in the sea.