Project description: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.
2024-08-10 | PXD045743 | Pride
Project description:Free-Living vs. Aggregate-Associated Heterotrophic Diazotrophs: Characteristics and Contribution to N2 Fixation in a Eutrophic River
Project description:Untargeted proteomics from a 5,000 km+ transect across the central Pacific Ocean from Hawaii to Tahiti. The expedition crossed multiple biogeochemical provinces, inlcuding the oligotrophic North Pacific Subtropical Gyre, the extremety of the Eastern Tropical North Pacific Oxygen Deficient Zone, and the relatively productive equatorial region associated with upwelling. This dataset focuses on the microbial fraction (0.2-3.0 micrometer filter size) and the microbial community dynamics across these biogeochemical provinces, from the surface oceance to the mesopelagic (1,250 m depth maximum).
Project description:We designed a new specific mRNA microarray targeting a subset of genes (956) of the diazotrophs Richelia intracellularis and Calothrix rhizosoleniae (genomes RintRC01, RintHH01, RintHM01 and CalSC01) which associate with diatom hosts. The aim was to be able to describe the gene expressions of genes related to several metabolic pathways, specifically nitrogen fixation and how they possibly differed between the closely related strains based on environment and host association. In this study we focused on the RintRC01 and RintHH01. To better understand how the gene expression of nitrogen fixation genes relates to nitrogen fixation rates both gene expression and rate measurements were done in parallell.
Project description:This project investigates the proteomic remodeling associated with N2 fixation and NH4+ assimilation in Zymomona mobilis. Previous work has elucidated the metabolic and proteomic response of Zymomona mobilis during steady state N2 fixation. These experiments examine the proteomic profile during the dynamic shift of N2 and NH4+.
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.
2023-06-07 | GSE234075 | GEO
Project description:Linking rhizospheric diazotrophs to the stimulation of soybean N2 fixation in a Mollisol amended with maize straw
| PRJNA626399 | ENA
Project description:Coastal N2 fixation of unicellular cyanobacteria
Project description:Investigation of whole genome gene expression level changes in two strains of the cyanobacteria Atelocyanobacterium thalasaa (UCYN-A) from environmental samples. The diel gene expression analyzed in this study is further described in Muñoz-Marin, M., I. N. Shilova, T. Shi, H. Farnelid & J. P. Zehr. 2017. Unicellular cyanobacterial symbiosis facilitates aerobic nitrogen fixation. Science (to be submitted).
2018-12-05 | GSE100124 | GEO
Project description:Methanotrophy induced N2-fixation in paddy soils