Nitrous oxide (N 2 O) synthesis by the freshwater cyanobacterium Microcystis aeruginosa

[摘要] Pure cultures of the freshwater cyanobacterium Microcystis aeruginosa synthesized nitrous oxide (N 2 O) when supplied with nitrite(NO 2 - ) 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 N 2 O productionwas negligible in abiotic controls supplied with NO 2 - and in cultures deprived of exogenous nitrogen. N 2 O production was alsopositively correlated to the initial NO 2 - and M. aeruginosa concentrations but waslow to negligible when nitrate (NO 3 - ) and ammonium(NH 4 + ) were supplied as the sole exogenous N source instead ofNO 2 - . A protein database search revealed that M. aeruginosa possesses proteinhomologous to eukaryotic microalgae enzymes known to catalyze the successivereduction of NO 2 - into nitric oxide (NO) and N 2 O. Ourlaboratory study is the first demonstration that M. aeruginosa possesses the ability tosynthesize N 2 O. As M. aeruginosa is a bloom-forming cyanobacterium found globally,further research (including field monitoring) is now needed to establish thesignificance of N 2 O synthesis by M. aeruginosa under relevant conditions (especiallyin terms of N supply). Further work is also needed to confirm thebiochemical pathway and potential function of this synthesis.

[学科分类] 大气科学