Dataset Information

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

ABSTRACT: The global significance of marine non-cyanobacterial diazotrophs, notably heterotrophic bacterial diazotrophs (HBDs), has become increasingly clear. Understanding N2 fixation rates for these largely uncultured organisms poses a challenge due to uncertain growth requirements and complex nitrogenase regulation. We identified Candidatus Thalassolituus haligoni as an Oceanospirillales member, closely related to other significant γ-proteobacterial HBDs. Pangenome analysis reinforces this classification, indicating the isolate belongs to the same species as the uncultured metagenome-assembled genome Arc-Gamma-03. Analysis of the nifH gene in amplicon sequencing libraries reveals the extensive distribution of Cand. T. haligoni across the Pacific, Atlantic and Arctic Oceans. Through combined proteomic analysis and N2 fixation rate measurements, we confirmed the isolate’s capacity for nitrate independent N2 fixation, although a clear understanding of nitrogenase regulation remains unclear. Overall, our study highlights the significance of Cand. T. haligoni as the first globally distributed, cultured model species within the understudied group of Oceanospirillales, and γ-HBDs in general.

INSTRUMENT(S): Orbitrap Fusion Lumos

ORGANISM(S): Environmental Samples <g-proteobacteria

TISSUE(S): Cell Culture

SUBMITTER: Elden Rowland

LAB HEAD: Erin Bertrand

PROVIDER: PXD045743 | Pride | 2024-08-10

REPOSITORIES: Pride

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Publications

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

Rose Sonja A SA Robicheau Brent M BM Tolman Jennifer J Fonseca-Batista Debany D Rowland Elden E Desai Dhwani D Ratten Jenni-Marie JM Kantor Ella Joy H EJH Comeau André M AM Langille Morgan G I MGI Jerlström-Hultqvist Jon J Devred Emmanuel E Sarthou Géraldine G Bertrand Erin M EM LaRoche Julie J

Science advances 20240731 31

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 N2 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 Oceanos ...[more]

PMID: 39083619

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Project description:Biological nitrogen fixation, the microbial reduction of atmospheric nitrogen to bioavailable ammonia, represents both a major limitation on biological productivity and a highly desirable engineering target for synthetic biology. However, the engineering of nitrogen fixation requires an integrated understanding of how the gene regulatory dynamics of host diazotrophs respond across sequence-function space of its central catalytic metalloenzyme, nitrogenase. Here, we interrogate this relationship by analyzing the transcriptome of Azotobacter vinelandii engineered with a phylogenetically inferred ancestral nitrogenase protein variant. The engineered strain exhibits reduced cellular nitrogenase activity but recovers wild-type growth rates following an extended lag period. We find that expression of genes within the immediate nitrogen fixation network is resilient to the introduced nitrogenase sequence-level perturbations. Rather the sustained physiological compatibility with the ancestral nitrogenase variant is accompanied by reduced expression of genes that support trace metal and electron resource allocation to nitrogenase. Our results spotlight gene expression changes in cellular processes adjacent to nitrogen fixation as productive engineering considerations to improve compatibility between remodeled nitrogenase proteins and engineered host diazotrophs. IMPORTANCE Azotobacter vinelandii is a key model bacterium for the study of biological nitrogen fixation, an important metabolic process catalyzed by nitrogenase enzymes. Here, we demonstrate that compatibilities between engineered A. vinelandii strains and nitrogenase variants can be modulated at the regulatory level. The engineered strain studied here responds by adjusting the expression of proteins involved in cellular processes adjacent to nitrogen fixation, rather than that of nitrogenase proteins themselves. These insights can inform future strategies to transfer nitrogenase variants to non-native hosts.

Dataset Information

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

Publications

Nitrogen fixation in the widely distributed marine γ-proteobacterial diazotroph <i>Candidatus</i> Thalassolituus haligoni.

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