Community Dynamics Localization and Fixation Potentials of Marine N2-Fixing Microbial Assemblages

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Chronic combined nitrogen deficiencies characterize vast segments of the world's oceans. Microbial nitrogen fixation helps to alleviate these deficiencies. The role of eubacteria as nitrogen fixers has received less attention than cyanobacteria. This project focuses on the role of eubacteria in N-depleted North Carolina coastal waters using recently developed immunological and molecular techniques to provide a cell specific set of fluorescence and isotopic assays of bacterial population and community dynamics in benthic and planktonic habitats. Such techniques and assays allow for identification of cells competent and induced to fix N, and provide a means to detect the presence of nitrogenase genes in total population DNA. These techniques will allow (1) direct, quantitative information on microbial N fixation potentials and sites thereof, (2) assessment of environmental conditions that regulate nitrogenase gene expression, and (3) evaluation of recently described, numerically and trophically important picoplanktonic cyanobacteria for their N fixing capabilities.