This work was funded by US-NSF grant #1434916: Photoheterotrophy in cyanobacteria: ecological drivers and significance for marine biogeochemistry  

Cyanobacteria are major contributors to primary production and carbon export in the open ocean. They also play an important role in the control of nutrient availability. The ability of these microbes to harvest light energy benefits a range of physiological functions, but the effect of light on their metabolism (other than for photosynthesis) is poorly known and controversial. This project investigates the role of light in uptake of organic substrates (carbon and nutrients) by marine cyanobacteria and elucidate the importance of photoheterotrophy. The ability of these organisms to assimilate organic compounds and its modulation by light and nutrients will provide additional hints about the ecological success of cyanobacteria in the ocean. The work involves field experiments in the southwest Pacific Ocean, complemented by laboratory experiments in controlled cultures of ecologically relevant cyanobacteria. The study employs innovative methods, including single cell assays and molecular tools that target individual cyanobacteria and evaluate their response to light for the assimilation of organic substrates. This research project aims to lead to an increased understanding of the microbial adaptations to light and nutrient gradients and the role these adaptations play in elemental cycling in oceanic habitats. 

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The grant has so far resulted in the following publications: 

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Benavides M., Duhamel S., Van Wambeke F., Shoemaker K.M., Moisander P.H., Salamon E., Riemann L., and S. Bonnet. 2020. Dissolved organic matter stimulates N2 fixation and nifH gene expression in Trichodesmium. FEMS Microbiology Letters, 367(4), fnaa034. doi.org/10.1093/femsle/fnaa034

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Berthelot H., Duhamel S., L’Helguen S., Maguer J.F., Wang S., and N. Cassar. 2019. NanoSIMS single cell analyses reveal the contrasting nitrogen sources for small phytoplankton. The ISME Journal 13:651–662,  doi: 10.1038/s41396-018-0285-8 Access here

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Duhamel, S. , Van Wambeke, F. , Lefevre, D. , Benavides, M. and S. Bonnet. 2018. Mixotrophic metabolism by natural communities of unicellular cyanobacteria in the western tropical South Pacific Ocean. Environ Microbiol. doi:10.1111/1462-2920.14111 Access here

​Dupouy C., Frouin R., Tedetti M., Maillard M., Rodier M., Lombard F., Guidi L., Picheral M., Duhamel S., Charrière B., and R. Sempéré. 2018. Diazotrophic Trichodesmium influence on ocean color and pigment composition in the South West tropical Pacific. Biogeosciences 15, 5249–5269, doi: 10.5194/bg-15-5249-2018. Access here

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Bock N.A., Van Wambeke F., Dion M., and S. Duhamel. 2018. Microbial community structure in the western tropical South Pacific. Biogeosciences, 15, 3909-3925, doi:10.5194/bg-15-3909-2018. Access here

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Van Wambeke, F., Gimenez, A., Duhamel, S., Dupouy, C., Lefevre, D., Pujo-Pay, M., and Moutin, T. (2018). Dynamics and controls of heterotrophic prokaryotic production in the western tropical South Pacific Ocean: links with diazotrophic and photosynthetic activity, Biogeosciences, 15, 2669-2689 Access here

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Benavides, M., Shoemaker, K. M., Moisander, P. H., Niggemann, J., Dittmar, T., Duhamel, S., Grosso, O., Pujo-Pay, M., Hélias-Nunige, S., Fumenia, A., and Bonnet, S. (2018). Aphotic N2 fixation along an oligotrophic to ultraoligotrophic transect in the western tropical South Pacific Ocean, Biogeosciences, 15, 3107-3119 Access here

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Rousselet L., de Verneil A., Doglioli A.M., Petrenko A.A., Duhamel S., Maes C., and B. Blanke. (2018). Large- to submesoscale surface circulation and its implications on biogeochemical/biological horizontal distributions during the OUTPACE cruise (southwest Pacific). Biogeosciences, 15, 2411–2431, doi: 10.5194/bg-15-2411-2018, 2018 Access here

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Benavides M., Berthelot H., Raimbault P., Duhamel S., S. Bonnet. (2017). Dissolved organic matter uptake by Trichodesmium in the Southwest Pacific. Nature Scientific Reports 7 : 41315, doi:10.1038/srep41315 Access here

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