Abstract
Diatoms are key contributors to global primary production, and have developed intricate partnerships with bacteria through long-term co-evolution. Here, we uncover a syntrophic relationship between the model obligate photoautotroph diatom Phaeodactylum tricornutum and the rod-shaped bacterium Loktanella vestfoldensis, which enables the diatom to indirectly utilize glucose. To be specific, growth of the diatom depends on the support of L. vestfoldensis for the supply of necessary carbon source when glucose serves as the sole carbon source, while L. vestfoldensis shows dependence on P. tricornutum when CO2 is the sole carbon source. Reanalysis of Tara Oceans metagenomic data shows frequent co-occurrence of Loktanella with diatoms including Chaetoceros and Thalassiosira, indicating the ecological relevance of this partnership. Co-culture with L. vestfoldensis supports robust growth of Chaetoceros muelleri and Thalassiosira pseudonana in the presence of glucose as the sole carbon source. Transcriptomic and metabolomic analyses reveal that P. tricornutum maintains a photoautotrophic metabolism in co-culture, as indicated by the up-regulation of genes involved in inorganic carbon concentration and photosynthesis, while the co-cultured bacterium likely supplies CO2 and growth-stimulating metabolites such as indole-3-acetic acid. Our findings demonstrate that bacterial-algal interactions may shape diatom adaptation to carbon changes and contribute to marine carbon cycling.
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Data availability
The raw data of RNA-Seq and 16S rRNA amplicon sequencing have been deposited in the Sequence Read Archive database under accession numbers PRJNA1276728 and PRJNA1330494. The Sanger sequencing data of 16S rRNA have been deposited in the Genbank database under accession numbers PX410800 (Janibacter anophelis) [https://www.ncbi.nlm.nih.gov/nuccore/PX410800] and PX410801 (Loktanella vestfoldensis) [https://www.ncbi.nlm.nih.gov/nuccore/PX410801]. The metabolomic data have been deposited on Metabolomics Workbench under Study ID ST004351 [https://doi.org/10.21228/M8WR9Z]. Source data are provided with this paper.
Code availability
The code used to produce the results is available at Figshare (https://doi.org/10.6084/m9.figshare.30178000).
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Acknowledgements
This work was funded by the National Key Research and Development Program of China with No. 2023YFA0914400 (2023YFA0914402 to H.H.) and National Natural Science Foundation of China with No. 42376131 (to H.H.). We acknowledge the Metabolomics Workbench (https://www.metabolomicsworkbench.org, supported by NIH grants U2C-DK119886 and OT2-OD030544) for hosting the data and metadata for this study (Study ID: ST004351).
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H.H. designed the research. C.L., W.Y., and Y.P. performed experiments and data analysis. C.L. and H.H. drafted the manuscript. H.H. revised the manuscript. H.H. acquired the financial support. All authors read and approved the final manuscript.
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Li, C., Yin, W., Pan, Y. et al. Interactions with bacteria shape diatom adaptation to carbon concentration changes. Nat Commun (2025). https://doi.org/10.1038/s41467-025-68050-3
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DOI: https://doi.org/10.1038/s41467-025-68050-3
