AUTORADIOGRAPHIC LOCALIZATION OF 13N AFTER FIXATION OF 13N-LABELED NITROGEN GAS BY A HETEROCYST-FORMING BLUE-GREEN ALGA |
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| Authors: | C Peter Wolk Sam M Austin John Bortins and Aaron Galonsky |
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| Institution: | From the MSU/AEC Plant Research Laboratory, and the Cyclotron Laboratory and the Department of Physics, Michigan State University, East Lansing, Michigan 48824. |
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| Abstract: | 13N, generated by proton bombardment of 13C powder, is rapidly and easily converted to 13N-N2, 0.01 atm pressure, ca. 10 mCi/ml, by automated Dumas combustion. 13N fixed (as 13N-N2) by algal filaments was localized by an autoradiographic technique which permits track autoradiography with isotopes having short half-lives. Our findings show directly that a minimum of about 25% of the N2 fixation by intact, aerobically grown filaments of Anabaena cylindrica is carried out by the heterocysts. If all of the N2 fixation takes place in the heterocysts, then the movement of nitrogen along the filaments can be characterized by a constant τ < ca. 5 s (cell-2). |
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