Journal
ENVIRONMENTAL SCIENCE & TECHNOLOGY
Volume 56, Issue 4, Pages 2760-2769Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.est.1c05279
Keywords
Anabaena variabilis ATCC 29413; acetylene reduction assay by cavity ring-down absorption spectroscopy; biological nitrogen fixation; nostocales; boreal forests
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Funding
- Canadian Research Chair in boreal biogeochemistry [CRC-950-230570]
- NSERC [RGPIN-2016-03660]
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This study characterizes the in vivo effect of temperature on the activities of Mo nitrogenase and V nitrogenase. It demonstrates that V nitrogenase becomes as efficient as Mo nitrogenase at temperatures below 10-15 degrees C. The availability of oxygen limits the activity of both enzymes at temperatures above 22 degrees C.
The reduction of atmospheric dinitrogen by nitrogenase is a key component of terrestrial nitrogen cycling. Nitrogenases exist in several isoforms named after the metal present within their active center: the molybdenum (Mo), the vanadium (V), and the iron (Fe)-only nitrogenase. While earlier in vitro studies hint that the relative contribution of V nitrogenase to total BNF could be temperature-dependent, the effect of temperature on in vivo activity remains to be investigated. In this study, we characterize the in vivo effect of temperature (3-42 degrees C) on the activities of Mo nitrogenase and V nitrogenase in the heterocystous cyanobacteria Anabaena variabilis ATTC 29413 using the acetylene reduction assay by cavity ring-down absorption spectroscopy. We demonstrate that V nitrogenase becomes as efficient as Mo nitrogenase at temperatures below 10-15 degrees C. At temperatures above 22 degrees C, BNF seems to be limited by O-2 availability to respiration in both enzymes. Furthermore, Anabaena variabilis cultures grown in Mo or V media achieved similar growth rates at temperatures below 20 degrees C. Considering the average temperature on earth is 15 degrees C, our findings further support the role of V nitrogenase as a viable backup enzymatic system for BNF in natural ecosystems.
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