@article{Chandola2025,

title = {A Bradyrhizobium isolate from a marine diatom induces nitrogen-fixing nodules in a terrestrial legume},

author = {Udita Chandola and Eric Manirakiza and Margaux Maillard and Louis-Josselin Lavier-Aydat and Alicia Camuel and Camille Trottier and Astuko Tanaka and Timothée Chaumier and Eric Giraud and Leila Tirichine},

editor = {Nature},

doi = {10.1038/s41564-025-02105-5},

year  = {2025},

date = {2025-09-05},

journal = {Nature Microbiology},

abstract = {Biological nitrogen fixation converts atmospheric nitrogen into ammonia, essential to the global nitrogen cycle. While cyanobacterial diazotrophs are well characterized, recent studies have revealed a broad distribution of non-cyanobacterial diazotrophs (NCDs) in marine environments, although their study is limited by poor cultivability. Here we report a previously uncharacterized Bradyrhizobium isolated from the marine diatom Phaeodactylum tricornutum. Phylogenomic analysis places the strain within photosynthetic Bradyrhizobium, suggesting evolutionary adaptations to marine and terrestrial niches. Average nucleotide identity supports its classification as a previously undescribed species. Remarkably, inoculation experiments showed that the isolate induced nitrogen-fixing nodules in the Aeschynomene indica legume, pointing to symbiotic capabilities across ecological boundaries. Pangenome analysis and metabolic predictions indicate that this isolate shares more features with terrestrial photosynthetic Bradyrhizobium than with marine NCDs. Overall, these findings suggest that symbiotic interactions could evolve across different ecological niches, and raise questions about the evolution of nitrogen fixation and microbe–host interactions.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Non-cyanobacterial diazotrophs support the survival of marine microalgae in nitrogen-depleted environment },

author = {Udita Chandola and Marinna Gaudin and Camille Trottier and Louis-Josselin Lavier-Aydat and Eric Manirakiza and Samuel Menicot and Erik Jörg Fischer and Isabelle Louvet and Thomas Lacour and Timothée Chaumier and Atsuko Tanaka and Georg Pohnert and Samuel Chaffron and Leïla Tirichine},

doi = {10.1186/s13059-025-03597-4},

year  = {2025},

date = {2025-05-15},

urldate = {2025-05-15},

journal = {Genome Biology},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {  Complete genome sequence of a marine Pseudoalteromonas bacterial strain},

author = {Eric Manirakiza and Timothée Chaumier and Leila Tirichine},

editor = {ASM Journals},

url = {https://journals.asm.org/doi/10.1128/mra.00975-24?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%20%200pubmed},

doi = {10.1128/mra.00975-24},

isbn = {39655917},

year  = {2025},

date = {2025-01-16},

urldate = {2025-01-16},

journal = {Microbiol Resour Announc .},

pages = {e0097524},

abstract = {Pseudoalteromonas is an abundant bacterial genera, found ubiquitously, including in extreme environments. Its broad metabolic capacity enables unique associations with various organisms. Using PacBio sequencing, we generated the complete genome sequence of a marine Pseudoalteromonas, revealing two circular chromosomes and one putative plasmid. The genome data are accessible at https://BacBrowse.univ-nantes.fr.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Genomic sequences and annotations of two Pseudomonas species isolated from marine and terrestrial habitats},

author = {Eric Manirakiza and Timothée Chaumier and Leïla Tirichine},

editor = {ASM Journals},

doi = { https://doi.org/10.1128/mra.00373-24},

year  = {2024},

date = {2024-08-27},

urldate = {2024-08-27},

journal = {Microbiol Resour Announc .},

pages = {e0037324},

abstract = {Here, we present the complete genome sequences and annotations of two species of the Pseudomonas genus isolated from marine and terrestrial environments. Both genomes and their annotations are available on BacBrowse (https://BacBrowse.univ-nantes.fr). This study will contribute to a better understanding of the diversity present within the Pseudomonas genus.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Hisanaga2023,

title = {The Polycomb repressive complex 2 deposits H3K27me3 and represses transposable elements in a broad range of eukaryotes},

author = {Tetsuya Hisanaga and Facundo Romani and Shuangyang Wu and Teresa Kowar and Yue Wu and Ruth Lintermann and Arie Fridrich and Chung Hyun Cho and Timothée Chaumier and Bhagyshree Jamge and Sean A Montgomery and Elin Axelsson and Svetlana Akimcheva and Tom Dierschke and John L Bowman and Takayuki Fujiwara and Shunsuke Hirooka and Shin-Ya Miyagishima and Liam Dolan and Leila Tirichine and Daniel Schubert and Frédéric Berger},

url = {https://www.sciencedirect.com/science/article/pii/S0960982223011533?via%3Dihub

hal-04284522v1},

doi = {10.1016/j.cub.2023.08.073},

year  = {2023},

date = {2023-08-02},

urldate = {2023-08-02},

journal = {Current Biology},

volume = {33},

issue = {20},

pages = {4367-4380.e9},

abstract = {The mobility of transposable elements (TEs) contributes to evolution of genomes. Their uncontrolled activity causes genomic instability; therefore, expression of TEs is silenced by host genomes. TEs are marked with DNA and H3K9 methylation, which are associated with silencing in flowering plants, animals, and fungi. However, in distantly related groups of eukaryotes, TEs are marked by H3K27me3 deposited by the Polycomb repressive complex 2 (PRC2), an epigenetic mark associated with gene silencing in flowering plants and animals. The direct silencing of TEs by PRC2 has so far only been shown in one species of ciliates. To test if PRC2 silences TEs in a broader range of eukaryotes, we generated mutants with reduced PRC2 activity and analyzed the role of PRC2 in extant species along the lineage of Archaeplastida and in the diatom P. tricornutum. In this diatom and the red alga C. merolae, a greater proportion of TEs than genes were repressed by PRC2, whereas a greater proportion of genes than TEs were repressed by PRC2 in bryophytes. In flowering plants, TEs contained potential cis-elements recognized by transcription factors and associated with neighbor genes as transcriptional units repressed by PRC2. Thus, silencing of TEs by PRC2 is observed not only in Archaeplastida but also in diatoms and ciliates, suggesting that PRC2 deposited H3K27me3 to silence TEs in the last common ancestor of eukaryotes. We hypothesize that during the evolution of Archaeplastida, TE fragments marked with H3K27me3 were selected to shape transcriptional regulation, controlling networks of genes regulated by PRC2.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Wu2023,

title = {PhaeoEpiView: an epigenome browser of the newly assembled genome of the model diatom Phaeodactylum tricornutum},

author = {Yue Wu and Timothée Chaumier and Eric Manirakiza and Alaguraj Veluchamy and Leila Tirichine},

url = {https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10206091/

hal-04284562v1 },

doi = { 10.1038/s41598-023-35403-1},

issn = {2045-2322},

year  = {2023},

date = {2023-05-23},

urldate = {2023-05-23},

journal = {Scientific Reports },

volume = {13},

pages = {8320},

abstract = {Recent advances in DNA sequencing technologies particularly long-read sequencing, greatly improved genomes assembly. However, this has created discrepancies between published annotations and epigenome tracks, which have not been updated to keep pace with the new assemblies. Here, we used the latest improved telomere-to-telomere assembly of the model pennate diatom Phaeodactylum tricornutum to lift over the gene models from Phatr3, a previously annotated reference genome. We used the lifted genes annotation and newly published transposable elements to map the epigenome landscape, namely DNA methylation and post-translational modifications of histones. This provides the community with PhaeoEpiView, a browser that allows the visualization of epigenome data and transcripts on an updated and contiguous reference genome, to better understand the biological significance of the mapped data. We updated previously published histone marks with a more accurate peak calling using mono instead of poly(clonal) antibodies and deeper sequencing. PhaeoEpiView (https://PhaeoEpiView.univ-nantes.fr) will be continuously updated with the newly published epigenomic data, making it the largest and richest epigenome browser of any stramenopile. In the upcoming era of molecular environmental studies, where epigenetics plays a significant role, we anticipate that PhaeoEpiView will become a widely used tool.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Chandola2022.08.25.505241,

title = {Combined in vivo and in situ genome-resolved metagenomics reveals novel symbiotic nitrogen fixing interactions between non-cyanobacterial diazotrophs and microalgae},

author = {Udita Chandola and Camille Trottier and Marinna Gaudin and Erik Manirakiza and Samuel Menicot and Isabelle Louvet and Thomas Lacour and Timothée Chaumier and Atsuko Tanaka and Samuel Chaffron and Leila Tirichine},

url = {https://www.biorxiv.org/content/early/2022/08/25/2022.08.25.505241},

doi = {10.1101/2022.08.25.505241},

year  = {2022},

date = {2022-08-25},

urldate = {2022-08-25},

journal = {bioRxiv},

publisher = {Cold Spring Harbor Laboratory},

abstract = {Non-cyanobacteria diazotrophs (NCDs) were shown to dominate in surface waters shifting the long-held paradigm of cyanobacteria dominance and raising fundamental questions on how these putative heterotrophic bacteria thrive in sunlit oceans. Here, we report an unprecedented finding in the widely used model diatom Phaeodactylum triconrnutum (Pt) of NCDs sustaining diatom cells in the absence of bioavailable nitrogen. We identified PtNCDs using metagenomics sequencing and detected nitrogenase gene in silico and/or by PCR. We demonstrated nitrogen fixation in PtNCDs and their close genetic affiliation with NCDs from the environment. We showed the wide occurrence of this type of symbiosis with the isolation of NCDs from other microalgae and their identification in the environment and in co-occurrence with photosynthetic microalgae. Overall, this study provides evidence for a previously overlooked symbiosis using a multidisciplinary model-based approach which will consequently help understand the different players driving global marine nitrogen fixation.Competing Interest StatementThe authors have declared no competing interest.},

keywords = {},

pubstate = {forthcoming},

tppubtype = {article}

}