The unique N2-fixation strategies in thermophilic Methanococcales

The metabolic capabilities of Methanothermococcus thermolithotrophicus make it a particularly attractive model: this thermophilic anaerobe is a gas bio-converter converting simultaneously inert N2 and CO2 into NH3 and CH4 biofuels. Considerable improvement of its cultivation conditions achieved in this study resulted in significantly higher cell yields, successfully used to establish N2-fixing bio-reactors. A detailed understanding of how N2-fixation is performed by this energy extremophile would provide new insights into its specific metabolic optimizations. The thermostable nitrogenase system of this archaeon belongs to an evolutionary group of yet uncharacterized nitrogenases. Our results show that diazotrophic growth of M. thermolithotrophicus is exclusively dependent on molybdenum and complementary transcriptomic profiling supports that it harbors a Mo-nitrogenase. Deeper analysis of these differentially expressed ORFs during diazotrophy and across three time-points provides new grounds for understanding the stress response to nitrogen limitation and its coordination with other metabolic processes.