Steady state growth under inorganic carbon limitation increases energy consumption for maintenance and enhances nitrous oxide production in Nitrosomonas europaea
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ABSTRACT: Nitrosomonas europaeais 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 ofN. europaeato 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 NH3to nitrite, depending on dilution rate and Na2CO3concentration. IC limitation resulted in a 2.3-fold increase in cellular maintenance energy requirements compared to 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 being 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 decreased expression of ammonium/ammonia transporter and ammonia monooxygenase subunits, and increased expression of genes involved in C1 metabolism including RuBisCO (cbbgene 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 NE0924-0927) correlated with increased production of N2O. Together, these data suggest thatN. europaeaadapts physiologically during IC-limited steady state growth, which leads to uncoupling of NH3oxidation from growth and increased N2O production. Transcriptome responses of N. europaea in 60 mM NH4+ to suboptimum levels of carbonate (1.0 mM and 0.2 mM) in continuous steady-state culture in a bioreactor.
ORGANISM(S): Nitrosomonas europaea
SUBMITTER: Luis Sayavedra-Soto
PROVIDER: E-GEOD-70988 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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