title: Global metabolomic responses of Nitrosomonas europaea 19718 to cold stress and altered ammonia feeding patterns.
abstract: The model ammonia-oxidizing bacterium Nitrosomonas europaea represents one of the environmentally and biotechnologically significant microorganisms. Genome-based studies over the last decade have led to many intriguing discoveries about its cellular biochemistry and physiology. However, knowledge regarding the regulation of overall metabolic routes in response to various environmental stresses is limited due to a lack of comprehensive, time-resolved metabolomic analyses. In this study, gas chromatography-mass spectrometry (GC-MS)-based metabolic profiling was performed to characterize the temporal variations of N. europaea 19718 intercellular metabolites in response to varied temperature (23 and 10 °C) and ammonia feeding patterns (shock loading and continuous feeding of 20 mg N/L). Approximately 87 metabolites were successfully identified and mapped to the existing pathways of N. europaea 19718, allowing interpretation of the influence of temperature and feeding pattern on metabolite levels. In general, varied temperature had a more profound influence on the overall metabolism than varied feeding patterns. Total extracellular metabolite concentrations (relative to internal standards and normalized to biomass weight) were lower under cold stress and shock loading conditions compared with the control (continuous feeding at 23 °C). Cold stress caused the widespread downregulation of metabolites involved in central carbon metabolism, amino acid, and lipid synthesis (e.g., malonic acid, succinic acid, putrescine, and phosphonolpyruvate). Metabolites that showed differences under varied feeding patterns were mainly involved in nucleotide acid, amino acid, and lipid metabolism (e.g., adenine, uracil, and spermidine). This study highlighted the roles of central carbon and nitrogen metabolism in countering cold stress and altered ammonia availability. In addition, transcriptomic, proteomic, and metabolomic data from three studies on N. europaea were compared to achieve a holistic view of some important synergy and interconnectivity among different cellular components (RNA, protein, and metabolites) during ammonia starvation.
authors.affiliation: Department of Civil and Environmental Engineering, University of Illinois at Urbana Champaign, 3207 Newmark Civil Engineering Laboratory, 205 N. Mathews Ave., Urbana, IL, 61801, USA. hlu2@uvm.edu.|Department of Civil and Environmental Engineering, University of Vermont, 33 Colchester ave, Votey 213E, Burlington, VT, 05405, USA. hlu2@uvm.edu.
authors.forename: Huijie
authors.initials: H
authors.lastname: Lu
authors.affiliation: Roy J. Carver Biotechnology Center, University of Illinois at Urbana Champaign, Urbana, IL, USA.
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Ulanov
authors.affiliation: Department of Civil and Environmental Engineering, University of Illinois at Urbana Champaign, 3207 Newmark Civil Engineering Laboratory, 205 N. Mathews Ave., Urbana, IL, 61801, USA.
authors.forename: Masaru
authors.initials: M
authors.lastname: Nobu
authors.affiliation: Department of Civil and Environmental Engineering, University of Illinois at Urbana Champaign, 3207 Newmark Civil Engineering Laboratory, 205 N. Mathews Ave., Urbana, IL, 61801, USA. wtliu@illinois.edu.
authors.forename: Wen-Tso
authors.initials: WT
authors.lastname: Liu
mesh_terms: D000641:Ammonia / Q000378:metabolism*; D003080:Cold Temperature; D008401:Gas Chromatography-Mass Spectrometry; D055442:Metabolome; D043370:Nitrosomonas europaea / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects*; D010084:Oxidation-Reduction
chemical_list: D000641:Ammonia
keywords: Feeding pattern; Integrated omics; Metabolomics; Nitrosomonas europaea; Temperature