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NITROGEN FIXATION, HYDROGEN CYCLING, AND ELECTRON TRANSPORT KINETICS IN TRICHODESMIUM ERYTHRAEUM (CYANOBACTERIA) STRAIN IMS101 1
Author(s) -
Wilson Samuel T.,
Kolber Zbigniew S.,
Tozzi Sasha,
Zehr Jonathan P.,
Karl David M.
Publication year - 2012
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/j.1529-8817.2012.01166.x
Subject(s) - trichodesmium , plastoquinone , dcmu , biology , photosynthesis , cyanobacteria , light intensity , electron transport chain , nitrogen fixation , nitrogenase , photosystem ii , botany , photochemistry , thylakoid , chemistry , biochemistry , diazotroph , chloroplast , bacteria , physics , gene , optics , genetics
This study describes the relationships between dinitrogen (N 2 ) fixation, dihydrogen (H 2 ) production, and electron transport associated with photosynthesis and respiration in the marine cyanobacterium Trichodesmium erythraeum Ehrenb. strain IMS101. The ratio of H 2 produced:N 2 fixed (H 2 :N 2 ) 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 N 2 fixation, as measured by acetylene reduction, saturated at light intensities of 200 μmol photons · m −2 · s −1 . In contrast, net H 2 production continued to increase with light levels up to 1,000 μmol photons · m −2 · s −1 . The H 2 :N 2 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 N 2 fixation and net H 2 production, while the H 2 :N 2 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 N 2 fixation and H 2 cycling in Trichodesmium indicate how light intensity and light spectral quality of the open ocean can influence the H 2 :N 2 ratio and modulate net H 2 production.