Quantifying nitrogen fixation by heterotrophic bacteria in sinking marine particles
Date of Original Version
Nitrogen (N 2) fixation by heterotrophic bacteria associated with sinking particles contributes to marine N cycling, but a mechanistic understanding of its regulation and significance are not available. Here we develop a mathematical model for unicellular heterotrophic bacteria growing on sinking marine particles. These bacteria can fix N 2 under suitable environmental conditions. We find that the interactive effects of polysaccharide and polypeptide concentrations, sinking speed of particles, and surrounding O 2 and NO3− concentrations determine the N 2 fixation rate inside particles. N 2 fixation inside sinking particles is mainly fueled by SO42− respiration rather than NO3− respiration. Our model suggests that anaerobic processes, including heterotrophic N 2 fixation, can take place in anoxic microenvironments inside sinking particles even in fully oxygenated marine waters. The modelled N 2 fixation rates are similar to bulk rates measured in the aphotic ocean, and our study consequently suggests that particle-associated heterotrophic N 2 fixation contributes significantly to oceanic N 2 fixation.
Publication Title, e.g., Journal
Chakraborty, Subhendu, Ken H. Andersen, André W. Visser, Keisuke Inomura, Michael J. Follows, and Lasse Riemann. "Quantifying nitrogen fixation by heterotrophic bacteria in sinking marine particles." Nature Communications 12, 1 (2021). doi: 10.1038/s41467-021-23875-6.