Abstract
Although nitric oxide (NO) emissions from anaerobic ammonium oxidation (anammox)-based processes were reported previously, the NO production pathways are poorly understood. Here, we investigated the NO production pathways in anammox granules in detail by combining 15N-stable isotope tracer experiments with various inhibitors, microsensor measurements, and transcriptome analysis for key genes of NO2- reduction. NO was emitted from the anammox granules, which account for 0.07% of the N2 emission. 15N-stable isotope-tracer experiments indicated that most of the N2 was produced by anammox bacteria, whereas NO was produced from NO2- reduction by anammox and denitrifying bacteria. The NO emission rate was highest at pH 8.0 and accelerated by increasing NH4+ and NO2- concentrations in the culture media. The microsensor analyses showed the in situ NO production rate was highest in the outer layer of the anammox granule where anammox activity was also highest. The detected in situ NO concentrations of up to 2.7 μM were significantly above physiological thresholds known to affect a wide range of microorganisms present in wastewater. Hence, NO likely plays pivotal roles in the microbial interactions in anammox granules, which needs to be further investigated.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 5744-5752 |
| Number of pages | 9 |
| Journal | Environmental Science and Technology |
| Volume | 52 |
| Issue number | 10 |
| DOIs | |
| State | Published - May 15 2018 |
Bibliographical note
Funding Information:Part of the bioinformatic analysis was done using the NIG supercomputer at ROIS National Institute of Genetics. This research was financially supported by the Japan Science and Technology Agency (JST) CREST Nagase Science and Technology Foundation, and the Institute for Fermentation Osaka (IFO), via grants to S.O. M.O. was supported by a grant-in-aid for JSPS Fellows from the Japan Society for the Promotion of Science.
Funding Information:
We thank Reiko Hirano and Ayumi Akiyoshi for technical assistance. Part of the bioinformatic analysis was done using the NIG supercomputer at ROIS National Institute of Genetics. This research was financially supported by the Japan Science and Technology Agency (JST) CREST, Nagase Science and Technology Foundation, and the Institute for Fermentation, Osaka (IFO), via grants to S.O. M.O. was supported by a grant-in-aid for JSPS Fellows from the Japan Society for the Promotion of Science.
Publisher Copyright:
© 2018 American Chemical Society.
