Nitrous Oxide Is a Potent Inhibitor of Bacterial Reductive Dechlorination

Journal Article · Tue Dec 18 00:00:00 EST 2018 · Environmental Science and Technology

DOI:https://doi.org/10.1021/acs.est.8b05871· OSTI ID:1490567

Yin, Yongchao ^[1]; Yan, Jun ^[2]; Chen, Gao ^[3]; Murdoch, Fadime Kara ^[1]; Pfisterer, Nina ^[4]; Löffler, Frank E.  ^[5]

---

1. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Microbiology and Center for Environmental Biotechnology; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Biosciences Division
2. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Microbiology; Chinese Academy of Sciences (CAS), Beijing (China). Key Lab. of Pollution Ecology and Environmental Engineering, Inst. of Applied Ecology
3. Univ. of Tennessee, Knoxville, TN (United States). Center for Environmental Biotechnology and Dept. of Civil and Environmental Engineering
4. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Microbiology and Center for Environmental Biotechnology; Bielefeld Univ., Bielefeld (Germany). RNA Biology and Molecular Physics
5. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Microbiology, Center for Environmental Biotechnology, Dept. of Civil and Environmental Engineering, and Dept. of Biosystems Engineering and Soil Science; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Biosciences Division

Organohalide-respiring bacteria are key players for the turnover of organohalogens. At sites impacted with chlorinated ethenes, bioremediation promotes reductive dechlorination; however, stoichiometric conversion to environmentally benign ethene is not always achieved. We demonstrate that nitrous oxide (N₂O), a compound commonly present in groundwater, inhibits organohalide respiration. N₂O concentrations in the low micromolar range decreased dechlorination rates and resulted in incomplete dechlorination of tetrachloroethene (PCE) in Geobacter lovleyi strain SZ and of cis-1,2-dichloroethene (cDCE) and vinyl chloride (VC) in Dehalococcoides mccartyi strain BAV₁ axenic cultures. Presumably, N₂O interferes with reductive dechlorination by reacting with super-reduced Co(I)–corrinoids of reductive dehalogenases, which is supported by the finding that N₂O did not inhibit corrinoid-independent fumarate-to-succinate reduction in strain SZ. Kinetic analyses revealed a best fit to the noncompetitive Michaelis–Menten inhibition model and determined N₂O inhibitory constants, K_I, for PCE and cDCE dechlorination of 40.8 ± 3.8 and 21.2 ± 3.5 μM in strain SZ and strain BAV₁, respectively. The lowest K_I value of 9.6 ± 0.4 μM was determined for VC to ethene reductive dechlorination in strain BAV₁, suggesting that this crucial dechlorination step for achieving detoxification is most susceptible to N₂O inhibition. Groundwater N₂O concentrations exceeding 100 μM are not uncommon, especially in watersheds impacted by nitrate runoff from agricultural sources. Thus, dissolved N₂O measurements can inform about cDCE and VC stalls at sites impacted with chlorinated ethenes.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 1490567
• Journal Information: Environmental Science and Technology, Vol. 53, Issue 2; ISSN 0013-936X
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES