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NITROGEN FIXATION, HYDROGEN CYCLING, AND ELECTRON TRANSPORT KINETICS IN TRICHODESMIUM ERYTHRAEUM (CYANOBACTERIA) STRAIN IMS1011
Article first published online: 3 MAY 2012
© 2012 Phycological Society of America
Journal of Phycology
Volume 48, Issue 3, pages 595–606, June 2012
How to Cite
Wilson, S. T., Kolber, Z. S., Tozzi, S., Zehr, J. P. and Karl, D. M. (2012), NITROGEN FIXATION, HYDROGEN CYCLING, AND ELECTRON TRANSPORT KINETICS IN TRICHODESMIUM ERYTHRAEUM (CYANOBACTERIA) STRAIN IMS101. Journal of Phycology, 48: 595–606. doi: 10.1111/j.1529-8817.2012.01166.x
Received: 12 May 2011. Accepted: 18 October 2011.
- Issue published online: 1 JUN 2012
- Article first published online: 3 MAY 2012
- Accepted manuscript online: 6 APR 2012 09:22PM EST
- nitrogen fixation;
This study describes the relationships between dinitrogen (N2) fixation, dihydrogen (H2) production, and electron transport associated with photosynthesis and respiration in the marine cyanobacterium Trichodesmium erythraeum Ehrenb. strain IMS101. The ratio of H2 produced:N2 fixed (H2:N2) was controlled by the light intensity and by the light spectral composition and was affected by the growth irradiance level. For Trichodesmium cells grown at 50 μmol photons · m−2 · s−1, the rate of N2 fixation, as measured by acetylene reduction, saturated at light intensities of 200 μmol photons · m−2 · s−1. In contrast, net H2 production continued to increase with light levels up to 1,000 μmol photons · m−2 · s−1. The H2:N2 ratios increased monotonically with irradiance, and the variable fluorescence measured using a fast repetition rate fluorometer (FRRF) revealed that this increase was accompanied by a progressive reduction of the plastoquinone (PQ) pool. Additions of 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB), an inhibitor of electron transport from PQ pool to PSI, diminished both N2 fixation and net H2 production, while the H2:N2 ratio increased with increasing level of PQ pool reduction. In the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), nitrogenase activity declined but could be prolonged by increasing the light intensity and by removing the oxygen supply. These results on the coupling of N2 fixation and H2 cycling in Trichodesmium indicate how light intensity and light spectral quality of the open ocean can influence the H2:N2 ratio and modulate net H2 production.