Impact of Fixed Nitrogen Availability on Dehalococcoides mccartyi Reductive Dechlorination Activity.
Devrim Kaya1,2, Birthe V Kjellerup2, Karuna Chourey
1Biosciences Division and ⊥Chemical Sciences Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States.
Environmental Science & Technology
|November 7, 2019
Summary
Adding ammonium (NH4+) can boost Dehalococcoides mccartyi (Dhc) growth and reductive dechlorination rates for chlorinated ethenes. However, relying on native nitrogen-fixing bacteria may achieve similar results without risks of inhibition.
Area of Science:
- Environmental Microbiology
- Bioremediation
- Geochemistry
Background:
- Biostimulation is used to enhance reductive dechlorination of chlorinated ethenes.
- The role of exogenous nitrogen (N) sources, like ammonium (NH4+), in this process is not fully understood.
- Dehalococcoides mccartyi (Dhc) are key microorganisms for reductive dechlorination.
Purpose of the Study:
- To investigate the impact of NH4+ availability on Dhc growth and reductive dechlorination.
- To compare the effectiveness of NH4+ addition versus relying on indigenous nitrogen-fixing bacteria.
- To understand the community-level responses to NH4+ amendment in contaminated environments.
Main Methods:
- Enrichment cultures from contaminated groundwater (PW4) and river sediment (TC).
- Quantitative polymerase chain reaction (qPCR) to assess Dhc populations.
- Analysis of Dhc nitrogenase genes, transcripts, and proteomics.
- In situ dechlorination activity assessment near well PW4.
Main Results:
- NH4+ addition significantly increased Dhc growth and cis-1,2-dichloroethene (cDCE) to ethene dechlorination rates in both PW4 and TC cultures.
- In PW4 cultures, NH4+ addition decreased the relative abundance of N2-fixing Cornell-type Dhc.
- NH4+ additions showed positive effects on in situ Dhc dechlorination activity.
- N2-fixing bacterial populations increased in incubations without NH4+.
Conclusions:
- Biostimulation with NH4+ can enhance Dhc-mediated reductive dechlorination rates.
- An alternative strategy of relying on indigenous diazotrophs can achieve comparable dechlorination outcomes.
- NH4+ addition may pose risks of stalled dechlorination due to inhibitory concentrations or transformation products like nitrous oxide.
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