Exogenous nitrate attenuates nitrite toxicity to anaerobic ammonium oxidizing (anammox) bacteria

Guangbin Li, David Vilcherrez, Jose Maria Carvajal-Arroyo, Maria Reye Sierra Alvarez, James A Field

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

Anaerobic ammonium oxidizing bacteria (anammox) can be severely inhibited by one of its main substrates, nitrite (NO2 -). At present, there is limited information on the processes by which anammox bacteria are able to tolerate toxic NO2 -. Intracellular consumption or electrochemically driven (transmembrane proton motive force) NO2 - export are considered the main mechanisms of NO2 - detoxification. In this work, we evaluated the potential of exogenous nitrate (NO3 -) on relieving NO2 - toxicity, putatively facilitated by NarK, a NO3 -/NO2 - transporter encoded in the anammox genome. The relative contribution of NO3 - to NO2 - detoxification was found to be pH dependent. Exposure of anammox cells to NO2 - in absence of their electron donating substrate, ammonium (NH4 +), causes NO2 - stress. At pH 6.7 and 7.0, the activity of NO2 - stressed cells was respectively 0 and 27% of the non-stressed control activity (NO2 - and NH4 + fed simultaneously). Exogenous NO3 - addition caused the recovery to 42% and 80% of the control activity at pH 6.7 and 7.0, respectively. The recovery of the activity of NO2 - stressed cells improved with increasing NO3 - concentration, the maximum recovery being achieved at 0.85 mM. The NO3 - pre-incubation time is less significant at pH 7.0 than at pH 6.7 due to a more severe NO2 - toxicity at lower pH. Additionally, NO3 - caused almost complete attenuation of NO2 - toxicity in cells exposed to the proton gradient disruptor carbonyl cyanide m-chlorophenyl hydrazone at pH 7.5, providing evidence that the NO3 - attenuation is independent of the proton motive force. The absence of a measurable NO3 - consumption (or NO3 - dependent N2 production) during the batch tests leaves NO3 - dependent active transport of NO2 - as the only plausible explanation for the relief of NO2 - inhibition. We suggest that anammox cells can use a secondary transport system facilitated by exogenous NO3 - to alleviate NO2 - toxicity.

Original languageEnglish (US)
Pages (from-to)2360-2367
Number of pages8
JournalChemosphere
Volume144
DOIs
StatePublished - Feb 1 2016

Keywords

  • Detoxification
  • Mechanism
  • Nitrate
  • Nitrite inhibition
  • Nitrogen removal

ASJC Scopus subject areas

  • Environmental Chemistry
  • Chemistry(all)

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