Nitrogen fixation in the widely distributed marine γ-proteobacterial diazotroph Candidatus Thalassolituus haligoni

The high diversity and global distribution of heterotrophic bacterial diazotrophs (HBDs) in the ocean has recently become apparent. However, understanding the role these largely uncultured microorganisms play in marine N 2 fixation poses a challenge due to their undefined growth requirements and the...

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Bibliographic Details
Published in:Science Advances
Main Authors: Rose, Sonja A., Robicheau, Brent M., Tolman, Jennifer, Fonseca-batista, Debany, Rowland, Elden, Desai, Dhwani, Ratten, Jenni-marie, Kantor, Ella Joy H., Comeau, André M., Langille, Morgan G.i., Jerlström-hultqvist, Jon, Devred, Emmanuel, Sarthou, Geraldine, Bertrand, Erin M., Laroche, Julie
Format: Article in Journal/Newspaper
Language:English
Published: American Association for the Advancement of Science (AAAS) 2024
Subjects:
Arctic
Arctic Ocean
Pacific
Online Access:https://archimer.ifremer.fr/doc/00903/101473/112290.pdf
https://archimer.ifremer.fr/doc/00903/101473/112293.pdf
https://archimer.ifremer.fr/doc/00903/101473/112294.zip
https://doi.org/10.1126/sciadv.adn1476
https://archimer.ifremer.fr/doc/00903/101473/
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Summary:The high diversity and global distribution of heterotrophic bacterial diazotrophs (HBDs) in the ocean has recently become apparent. However, understanding the role these largely uncultured microorganisms play in marine N 2 fixation poses a challenge due to their undefined growth requirements and the complex regulation of the nitrogenase enzyme. We isolated and characterized Candidatus Thalassolituus haligoni, a member of a widely distributed clade of HBD belonging to the Oceanospirillales. Analysis of its nifH gene via amplicon sequencing revealed the extensive distribution of Cand. T. haligoni across the Pacific, Atlantic, and Arctic Oceans. Pangenome analysis indicates that the isolate shares >99% identity with an uncultured metagenome-assembled genome called Arc-Gamma-03, recently recovered from the Arctic Ocean. Through combined genomic, proteomic, and physiological approaches, we confirmed that the isolate fixes N 2 gas. However, the mechanisms governing nitrogenase regulation in Cand. T. haligoni remain unclear. We propose Cand. T. haligoni as a globally distributed, cultured HBD model species within this understudied clade of Oceanospirillales.

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