NITROGENASE CONFINED TO RANDOMLY DISTRIBUTED TRICHOMES IN THE MARINE CYANOBACTERIUM TRICHODESMIUM THIEBAUTII

Authors


  • Received 30 July 1990. Accepted 26 November 1990.

  • Financial support was received from the Swedish Natural Sciences Research Council (to B.B.) and the Ocean Sciences Division of the U.S. National Science Foundation (to E.J.C.). Technical assistance of A. Axén, E. Danielsson, and K. Österlund is acknowledged.

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ABSTRACT

Nitrogenase reductase (Fe-protein) was detected in the marine planktonic cyanobacterium Trichodesmium. The molecular weight was about 38 kD, as shown by western blotting using anti -Rhodospirillum rubrum nitrogenase reductase antiserum. The enzyme was confined to a limited number (ca. 10–40%) of randomly distributed trichomes in the Trichodesmium colonies, as shown by immunogold localization and transmission electron microscopy. Associated microorganisms had little or no nitrogenase. Nitrogenase showed a diel cycle in localization: present throughout the cytoplasm of cells in N2-fixing (daytime) colonies but at the periphery of non-N2-fixing (nighttime) colonies. This structural arrangement of N2-fixing trichomes and nitrogenase is novel and different from the previously held paradigm for this and other diazotrophic cyanobacteria.

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