Active nitrogen fixation by Crocosphaera expands their niche despite the presence of ammonium – A case study

Abstract Unicellular nitrogen fixer Crocosphaera contributes substantially to nitrogen fixation in oligotrophic subtropical gyres. They fix nitrogen even when significant amounts of ammonium are available. This has been puzzling since fixing nitrogen is energetically inefficient compared with using...

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Autores principales:	Keisuke Inomura, Takako Masuda, Julia M. Gauglitz
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2019
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/ce7c1f9e283e4f8ea6b26d86f1315633
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spelling	oai:doaj.org-article:ce7c1f9e283e4f8ea6b26d86f13156332021-12-02T15:08:08ZActive nitrogen fixation by Crocosphaera expands their niche despite the presence of ammonium – A case study10.1038/s41598-019-51378-42045-2322https://doaj.org/article/ce7c1f9e283e4f8ea6b26d86f13156332019-10-01T00:00:00Zhttps://doi.org/10.1038/s41598-019-51378-4https://doaj.org/toc/2045-2322Abstract Unicellular nitrogen fixer Crocosphaera contributes substantially to nitrogen fixation in oligotrophic subtropical gyres. They fix nitrogen even when significant amounts of ammonium are available. This has been puzzling since fixing nitrogen is energetically inefficient compared with using available ammonium. Here we show that by fixing nitrogen, Crocosphaera can increase their population and expand their niche despite the presence of ammonium. We have developed a simple but mechanistic model of Crocosphaera based on their growth in steady state culture. The model shows that the growth of Crocosphaera can become nitrogen limited despite their capability to fix nitrogen. When they fix nitrogen, the population increases by up to 78% relative to the case without nitrogen fixation. When we simulate a simple ecological situation where Crocosphaera exists with non-nitrogen-fixing phytoplankton, the relative abundance of Crocosphaera increases with nitrogen fixation, while the population of non-nitrogen-fixing phytoplankton decreases since a larger fraction of fixed nitrogen is consumed by Crocosphaera. Our study quantitatively supports the benefit of nitrogen fixation despite the high electron/energy costs, even when an energetically efficient alternative is available. It demonstrates a competitive aspect of Crocosphaera, permitting them to be regionally significant nitrogen fixers.Keisuke InomuraTakako MasudaJulia M. GauglitzNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 9, Iss 1, Pp 1-11 (2019)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Keisuke Inomura Takako Masuda Julia M. Gauglitz Active nitrogen fixation by Crocosphaera expands their niche despite the presence of ammonium – A case study
description	Abstract Unicellular nitrogen fixer Crocosphaera contributes substantially to nitrogen fixation in oligotrophic subtropical gyres. They fix nitrogen even when significant amounts of ammonium are available. This has been puzzling since fixing nitrogen is energetically inefficient compared with using available ammonium. Here we show that by fixing nitrogen, Crocosphaera can increase their population and expand their niche despite the presence of ammonium. We have developed a simple but mechanistic model of Crocosphaera based on their growth in steady state culture. The model shows that the growth of Crocosphaera can become nitrogen limited despite their capability to fix nitrogen. When they fix nitrogen, the population increases by up to 78% relative to the case without nitrogen fixation. When we simulate a simple ecological situation where Crocosphaera exists with non-nitrogen-fixing phytoplankton, the relative abundance of Crocosphaera increases with nitrogen fixation, while the population of non-nitrogen-fixing phytoplankton decreases since a larger fraction of fixed nitrogen is consumed by Crocosphaera. Our study quantitatively supports the benefit of nitrogen fixation despite the high electron/energy costs, even when an energetically efficient alternative is available. It demonstrates a competitive aspect of Crocosphaera, permitting them to be regionally significant nitrogen fixers.
format	article
author	Keisuke Inomura Takako Masuda Julia M. Gauglitz
author_facet	Keisuke Inomura Takako Masuda Julia M. Gauglitz
author_sort	Keisuke Inomura
title	Active nitrogen fixation by Crocosphaera expands their niche despite the presence of ammonium – A case study
title_short	Active nitrogen fixation by Crocosphaera expands their niche despite the presence of ammonium – A case study
title_full	Active nitrogen fixation by Crocosphaera expands their niche despite the presence of ammonium – A case study
title_fullStr	Active nitrogen fixation by Crocosphaera expands their niche despite the presence of ammonium – A case study
title_full_unstemmed	Active nitrogen fixation by Crocosphaera expands their niche despite the presence of ammonium – A case study
title_sort	active nitrogen fixation by crocosphaera expands their niche despite the presence of ammonium – a case study
publisher	Nature Portfolio
publishDate	2019
url	https://doaj.org/article/ce7c1f9e283e4f8ea6b26d86f1315633
work_keys_str_mv	AT keisukeinomura activenitrogenfixationbycrocosphaeraexpandstheirnichedespitethepresenceofammoniumacasestudy AT takakomasuda activenitrogenfixationbycrocosphaeraexpandstheirnichedespitethepresenceofammoniumacasestudy AT juliamgauglitz activenitrogenfixationbycrocosphaeraexpandstheirnichedespitethepresenceofammoniumacasestudy
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Active nitrogen fixation by Crocosphaera expands their niche despite the presence of ammonium – A case study

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