Laboratory Culture and Preliminary Characterization of the Nitrogen-Fixing Rhizosolenia-Richelia Symbiosis |
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| Authors: | Tracy A Villareal |
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| Institution: | Graduate School of Oceanography, University of Rhode Island, Kingston, RI, U. S. A. 02881 |
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| Abstract: | Abstract. The oceanic diatom Rhizosolenia clevei and its cyanobactcrial symbiont Richelia intracel-luluris were isolated into laboratory culture and their biology and growth dynamics examined. Nitrogen-fixation by the symbiont could sustain the symbiosis. Growth and nitrogenase activity demonstrated light saturation kinetics, with no photoinhibition up to 315 μE m-1 s-1 for growth and 780μE m-1 s-1 for nitrogen fixation. The symbiosis is not obligate for Rhizosolenia , which is capable of growth independent of the symbiont if a nitrogen source is available. The symbiont is contained in the pcriplasmic space between the Rhizosolenia plasmalcmma and frustulc, and preliminary evidence suggests excretion of fixed nitrogen into the medium may be occurring. |
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| Keywords: | Culture media cyanobacteria diatoms diazotrophy nitrogen-fixation phytoplankton Rhizosolenia Richelia symbiosis |
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