Global Isotope Metabolomics Reveals Adaptive Strategies for Nitrogen Assimilation

摘要

Nitrogen 'cycling is a microbial :metabolicprocess essential for Vobal ecologicaliagricoltiral balance. To investigate the link between the well-established otrooniun and the alternative nitrate assimilation -metabolic- pathways, global' isotope metabolomics, was employed, to :examine three nitrate reducing bacteria using (NO3)-N-15 as, a nitrogen source: In contrast to a control (Pseudomonas stn tzeri RCH2), the "results show that two,of -the isolates from Oak Ridge,,Tennessee (Pseudomonas N2A2 and N2E2) utilize nitrate, and ammonia for assiniilationconc-nrrently with differential Jabeling observed- across multiple classes of metabolites including amino acids and nucleotides. The -data -reveal that the N2A2 arid N2E2 strains conserve nitrogen -containing metabolitesi-iridicating--that the nitrate assimilation pathway is a conservation inechanism for the assimilation of nitrogen. Co -utilization of nitrate arid ammonia is likely an adaption to manage higher levels of nitrite since the denitrificotiori pathways utilized by the N2A2 and N2E2 strains from the Oak Ridge siteare preclispo'sed to the accumulation of the toxic nitrite. The use Of global- isotope metabolomics allowed for "tbi, s adaptive strategy to be investigated, which Would otherwise not have' been possible to decipher: