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Nitrogen fixation, hydrogen cycling, and electron transport kinetics in trichodesmium erythraeum (cyanobacteria) strain ims101

Lookup NU author(s): Professor Sam Wilson

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Abstract

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 50μmol photons·m-2·s-1, the rate of N2 fixation, as measured by acetylene reduction, saturated at light intensities of 200μmol photons·m-2·s-1. In contrast, net H2 production continued to increase with light levels up to 1,000μmol 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. © 2012 Phycological Society of America.

Publication metadata

Author(s): Wilson ST, Kolber ZS, Tozzi S, Zehr JP, Karl DM

Publication type: Article

Publication status: Published

Journal: Journal of Phycology

Year: 2012

Volume: 48

Issue: 3

Pages: 595-606

Print publication date: 01/06/2012

Online publication date: 06/04/2012

ISSN (print): 0022-3646

ISSN (electronic): 1529-8817

Publisher: Blackwell Publishing Inc.

URL: https://doi.org/10.1111/j.1529-8817.2012.01166.x

DOI: 10.1111/j.1529-8817.2012.01166.x

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