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Evaluation of argon‐induced hydrogen production as a method to measure nitrogen fixation by cyanobacteria
Author(s) -
Wilson Samuel T.,
Caffin Mathieu,
White Angelicque E.,
Karl David M.
Publication year - 2021
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/jpy.13129
Subject(s) - nitrogenase , cyanobacteria , nitrogen fixation , biology , carbon fixation , hydrogen , nitrogen , argon , carbon dioxide , context (archaeology) , hydrogen production , photosynthesis , botany , biochemistry , chemistry , ecology , bacteria , organic chemistry , paleontology , genetics , catalysis
The production of dihydrogen (H 2 ) is an enigmatic yet obligate component of biological dinitrogen (N 2 ) fixation. This study investigates the effect on H 2 production by N 2 fixing cyanobacteria when they are exposed to either air or a gas mixture consisting of argon, oxygen, and carbon dioxide (Ar:O 2 :CO 2 ). In the absence of N 2 , nitrogenase diverts the flow of electrons to the production of H 2 , which becomes a measure of Total Nitrogenase Activity (TNA). This method of argon‐induced hydrogen production (AIHP) is much less commonly used to infer rates of N 2 fixation than the acetylene reduction (AR) assay. We provide here a full evaluation of the AIHP method and demonstrate its ability to achieve high‐resolution measurements of TNA in a gas exchange flow‐through system. Complete diel profiles of H 2 production were obtained for N 2 fixing cyanobacteria despite the absence of N 2 that broadly reproduced the temporal patterns observed by the AR assay. Comparison of H 2 production under air versus Ar:O 2 :CO 2 revealed the efficiency of electron usage during N 2 fixation and place these findings in the broader context of cell metabolism. Ultimately, AIHP is demonstrated to be a viable alternative to the AR assay with several additional merits that provide an insight into cell physiology and promise for successful field application.