Fabisik FGuieysse BProcter JPlouviez MTreude TBouillon S2025-01-132025-01-132023-02-13Fabisik F, Guieysse B, Procter J, Plouviez M. (2023). Nitrous oxide (N2O) synthesis by the freshwater cyanobacterium Microcystis aeruginosa. Biogeosciences. 20. 3. (pp. 687-693).1726-4170https://mro.massey.ac.nz/handle/10179/72365Pure cultures of the freshwater cyanobacterium Microcystis aeruginosa synthesized nitrous oxide (N2O) when supplied with nitrite (NO2-) in darkness (198.9 nmol g-DW-1 h-1 after 24 h) and illumination (163.1 nmol g-DW-1 h-1 after 24 h), whereas N2O production was negligible in abiotic controls supplied with NO2- and in cultures deprived of exogenous nitrogen. N2O production was also positively correlated to the initial NO2- and M. aeruginosa concentrations but was low to negligible when nitrate (NO3-) and ammonium (NH4+) were supplied as the sole exogenous N source instead of NO2-. A protein database search revealed that M. aeruginosa possesses protein homologous to eukaryotic microalgae enzymes known to catalyze the successive reduction of NO2- into nitric oxide (NO) and N2O. Our laboratory study is the first demonstration that M. aeruginosa possesses the ability to synthesize N2O. As M. aeruginosa is a bloom-forming cyanobacterium found globally, further research (including field monitoring) is now needed to establish the significance of N2O synthesis by M. aeruginosa under relevant conditions (especially in terms of N supply). Further work is also needed to confirm the biochemical pathway and potential function of this synthesis.(c) 2023 The Author/sCC BY 4.0https://creativecommons.org/licenses/by/4.0/Journal article10.5194/bg-20-687-20231726-4189journal-article687-693