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  • Nitrosomonas europaea is a chemolithoautotrophic bacterium that oxidizes ammonia (NH₃) to obtain energy for growth on carbon dioxide (CO₂) and can also produce nitrous oxide (N₂O), a greenhouse gas. We interrogated the growth, physiological, and transcriptome responses of N. europaea to conditions of replete (>5.2 mM) and limited inorganic carbon (IC) provided by either 1.0 mM or 0.2 mM sodium carbonate (Na₂CO₃) supplemented with atmospheric CO₂. IC-limited cultures oxidized 25 to 58% of available NH₃ to nitrite, depending on the dilution rate and Na₂CO₃ concentration. IC limitation resulted in a 2.3-fold increase in cellular maintenance energy requirements compared to those for NH₃-limited cultures. Rates of N₂O production increased 2.5- and 6.3-fold under the two IC-limited conditions, increasing the percentage of oxidized NH₃-N that was transformed to N₂O-N from 0.5% (replete) up to 4.4% (0.2 mM Na₂CO₃). Transcriptome analysis showed differential expression (P ≤ 0.05) of 488 genes (20% of inventory) between replete and IC-limited conditions, but few differences were detected between the two IC-limiting treatments. IC-limited conditions resulted in a decreased expression of ammonium/ammonia transporter and ammonia monooxygenase subunits and increased the expression of genes involved in C₁ metabolism, including the genes for RuBisCO (cbb gene cluster), carbonic anhydrase, folate-linked metabolism of C₁ moieties, and putative C salvage due to oxygenase activity of RuBisCO. Increased expression of nitrite reductase (gene cluster NE0924 to NE0927) correlated with increased production of N₂O. Together, these data suggest that N. europaea adapts physiologically during IC-limited steady-state growth, which leads to the uncoupling of NH₃ oxidation from growth and increased N₂O production. IMPORTANCE: Nitrification, the aerobic oxidation of ammonia to nitrate via nitrite, is an important process in the global nitrogen cycle. This process is generally dependent on ammonia-oxidizing microorganisms and nitrite-oxidizing bacteria. Most nitrifiers are chemolithoautotrophs that fix inorganic carbon (CO₂) for growth. Here, we investigate how inorganic carbon limitation modifies the physiology and transcriptome of Nitrosomonas europaea, a model ammonia-oxidizing bacterium, and report on increased production of N₂O, a potent greenhouse gas. This study, along with previous work, suggests that inorganic carbon limitation may be an important factor in controlling N₂O emissions from nitrification in soils and wastewater treatment.
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  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2016-06-24T18:46:38Z (GMT) No. of bitstreams: 3 MellbyeSteadyStateGrowth.pdf: 803569 bytes, checksum: 15f72a77da8bab3d6ec9b295204d1e39 (MD5) MellbyeSteadyStateGrowthSupp1.pdf: 850498 bytes, checksum: 057919af1f6e1b86d76adda34690d9ff (MD5) MellbyeSteadyStateGrowthSupp2.xls: 1394176 bytes, checksum: 5e8bd397972510edc18976677687a55c (MD5)
  • description.provenance : Made available in DSpace on 2016-06-24T18:46:38Z (GMT). No. of bitstreams: 3 MellbyeSteadyStateGrowth.pdf: 803569 bytes, checksum: 15f72a77da8bab3d6ec9b295204d1e39 (MD5) MellbyeSteadyStateGrowthSupp1.pdf: 850498 bytes, checksum: 057919af1f6e1b86d76adda34690d9ff (MD5) MellbyeSteadyStateGrowthSupp2.xls: 1394176 bytes, checksum: 5e8bd397972510edc18976677687a55c (MD5) Previous issue date: 2016-06
  • description.provenance : Submitted by Patricia Black (patricia.black@oregonstate.edu) on 2016-06-24T18:46:22Z No. of bitstreams: 3 MellbyeSteadyStateGrowth.pdf: 803569 bytes, checksum: 15f72a77da8bab3d6ec9b295204d1e39 (MD5) MellbyeSteadyStateGrowthSupp1.pdf: 850498 bytes, checksum: 057919af1f6e1b86d76adda34690d9ff (MD5) MellbyeSteadyStateGrowthSupp2.xls: 1394176 bytes, checksum: 5e8bd397972510edc18976677687a55c (MD5)

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