@article{221, keywords = {Desulfovibrio vulgaris var. Hildenborough Biological nitrogen fixation Anaerobic heterotroph Benthic sediments biogeochemistry Quantitative model}, author = {R. *Darnajoux and K. Inomura and X. Zhang}, title = {A diazotrophy-ammoniotrophy dual growth model for the sulfate reducing bacterium Desulfovibrio vulgaris var. Hildenborough}, abstract = {

Sulfate reducing bacteria (SRB) comprise one of the few prokaryotic groups in which biological nitrogen fixation (BNF) is common. Recent studies have highlighted SRB roles in N cycling, particularly in oligotrophic coastal and benthic environments where they could contribute significantly to N input. Most studies of SRB have focused on sulfur cycling and SRB growth models have primarily aimed at understanding the effects of electron sources, with N usually provided as fixed-N (nitrate, ammonium). Mechanistic links between SRB nitrogen-fixing metabolism and growth are not well understood, particularly in environments where fixed-N fluctuates. Here, we investigate diazotrophic growth of the model sulfate reducer Desulfovibrio vulgaris var. Hildenborough under anaerobic heterotrophic conditions and contrasting N availabilities using a simple cellular model with dual ammoniotrophic and diazotrophic modes. The model was calibrated using batch culture experiments with varying initial ammonium concentrations (0{\textendash}3000\ {\textmu}M) and acetylene reduction assays of BNF activity. The model confirmed the preferential usage of ammonium over BNF for growth and successfully reproduces experimental data, with notably clear bi-phasic growth curves showing an initial ammoniotrophic phase followed by onset of BNF. Our model enables quantification of the energetic cost of each N acquisition strategy and indicates the existence of a BNF-specific limiting phenomenon, not directly linked to micronutrient (Mo, Fe, Ni) concentration, by-products (hydrogen, hydrogen sulfide), or fundamental model metabolic parameters (death rate, electron acceptor stoichiometry). By providing quantitative predictions of environment and metabolism, this study contributes to a better understanding of anaerobic heterotrophic diazotrophs in environments with fluctuating N conditions.

}, year = {2023}, journal = {Computational and Structural Biotechnology Journal}, volume = {21}, chapter = {3136}, pages = {3136-3148}, url = {https://doi.org/10.1016/j.csbj.2023.05.007}, doi = {10.1016/j.csbj.2023.05.007}, }