The Calcidiscus leptoporus genome reveals vitamin-mediated holobiont interactions
Abstract
Coccolithophores are major marine phytoplankton that contribute to ocean carbon cycling through both organic carbon fixation and calcium carbonate biomineralization, yet the functional basis of their interactions with phycosphere bacteria remains poorly resolved. Here, we present the nuclear genome of the haploid phase of the coccolithophore Calcidiscus leptoporus, a coccolithophore that calcifies in both life-cycle stages. We combined host genome analysis, genome-resolved characterization of associated bacteria, and a four-month vitamin-manipulation experiment to test how B-vitamin biosynthetic complementarity relates to host performance and phycosphere community assembly. Metabolic reconstructions indicate partitioned B-vitamin biosynthtic potential: the host encodes pathways for B2, B5, B6, and B9, including a rare fused B5 biosynthesis gene, but lacks complete pathways for B1, B3, B7, and B12. These missing functions were distributed among recurrent bacterial taxa, with no single bacterial MAG encoding the full set of host-missing vitamins. Across the experiment, bacterial community composition was structured primarily by the experimental phase, while vitamin treatments secondarily influenced which taxa became enriched at later stages. Consistent with genome-inferred auxotrophy, B-vitamin availability constrained long-term growth under the tested conditions, with B1 alone providing partial rescue and vitamin-replete treatments showing equal or stronger responses. Together, these data establish C. leptoporus as a genomic model for coccolithophore biology and holobiont interactions, while providing a testable framework linking vitamin economies to phycosphere assembly and host performance.
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BibTeX
@article{chaux2026calcidiscus,
title = {{The Calcidiscus leptoporus genome reveals vitamin-mediated holobiont interactions}},
author = {Frederic Chaux and Tanja Vojvoda Zeljko and Borna Branimir Vuković and John Burns and Titouan Le Perrun and Marta Žižek and Briget Bannerman and Donald Tonye Bara Mason and Clotilde Garrido and Zhou Xu and Richard Dorrell and Jelena Godrijan},
journal = {ISME Communications},
year = {2026},
month = aug,
doi = {10.1093/ismeco/ycag222},
url = {https://hal.science/hal-05842426v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - The Calcidiscus leptoporus genome reveals vitamin-mediated holobiont interactions
AU - Frederic Chaux
AU - Tanja Vojvoda Zeljko
AU - Borna Branimir Vuković
AU - John Burns
AU - Titouan Le Perrun
AU - Marta Žižek
AU - Briget Bannerman
AU - Donald Tonye Bara Mason
AU - Clotilde Garrido
AU - Zhou Xu
AU - Richard Dorrell
AU - Jelena Godrijan
PY - 2026
DA - 2026/08/23
JO - ISME Communications
DO - 10.1093/ismeco/ycag222
UR - https://hal.science/hal-05842426v1
AB - Coccolithophores are major marine phytoplankton that contribute to ocean carbon cycling through both organic carbon fixation and calcium carbonate biomineralization, yet the functional basis of their interactions with phycosphere bacteria remains poorly resolved. Here, we present the nuclear genome of the haploid phase of the coccolithophore Calcidiscus leptoporus, a coccolithophore that calcifies in both life-cycle stages. We combined host genome analysis, genome-resolved characterization of associated bacteria, and a four-month vitamin-manipulation experiment to test how B-vitamin biosynthetic complementarity relates to host performance and phycosphere community assembly. Metabolic reconstructions indicate partitioned B-vitamin biosynthtic potential: the host encodes pathways for B2, B5, B6, and B9, including a rare fused B5 biosynthesis gene, but lacks complete pathways for B1, B3, B7, and B12. These missing functions were distributed among recurrent bacterial taxa, with no single bacterial MAG encoding the full set of host-missing vitamins. Across the experiment, bacterial community composition was structured primarily by the experimental phase, while vitamin treatments secondarily influenced which taxa became enriched at later stages. Consistent with genome-inferred auxotrophy, B-vitamin availability constrained long-term growth under the tested conditions, with B1 alone providing partial rescue and vitamin-replete treatments showing equal or stronger responses. Together, these data establish C. leptoporus as a genomic model for coccolithophore biology and holobiont interactions, while providing a testable framework linking vitamin economies to phycosphere assembly and host performance.
SN - 2730-6151
ER -