TY - JOUR
T1 - Impact of Fixed Nitrogen Availability on Dehalococcoides mccartyi Reductive Dechlorination Activity
AU - Kaya, Devrim
AU - Kjellerup, Birthe V.
AU - Chourey, Karuna
AU - Hettich, Robert L.
AU - Taggart, Dora M.
AU - Löffler, Frank E.
N1 - Publisher Copyright:
Copyright © 2019 American Chemical Society.
PY - 2019/12/17
Y1 - 2019/12/17
N2 - Biostimulation to promote reductive dechlorination is widely practiced, but the value of adding an exogenous nitrogen (N) source (e.g., NH4 +) during treatment is unclear. This study investigates the effect of NH4 + availability on organohalide-respiring Dehalococcoides mccartyi (Dhc) growth and reductive dechlorination in enrichment cultures derived from groundwater (PW4) and river sediment (TC) impacted with chlorinated ethenes. In PW4 cultures, the addition of NH4 + increased cis-1,2-dichloroethene (cDCE)-to-ethene dechlorination rates about 5-fold (20.6 ± 1.6 versus 3.8 ± 0.5 μM Cl- d-1), and the total number of Dhc 16S rRNA gene copies were about 43-fold higher in incubations with NH4 + ((1.8 ± 0.9) × 108 mL-1) compared to incubations without NH4 + ((4.1 ± 0.8) × 107 mL-1). In TC cultures, NH4 + also stimulated cDCE-to-ethene dechlorination and Dhc growth. Quantitative polymerase chain reaction (qPCR) revealed that Cornell-type Dhc capable of N2 fixation dominated PW4 cultures without NH4 +, but their relative abundance decreased in cultures with NH4 + amendment (i.e., 99 versus 54% of total Dhc). Pinellas-type Dhc incapable of N2 fixation were responsible for cDCE dechlorination in TC cultures, and diazotrophic community members met their fixed N requirement in the medium without NH4 +. Responses to NH4 + were apparent at the community level, and N2-fixing bacterial populations increased in incubations without NH4 +. Quantitative assessment of Dhc nitrogenase genes, transcripts, and proteomics data linked Cornell-type Dhc nifD and nifK expression with fixed N limitation. NH4 + additions also demonstrated positive effects on Dhc in situ dechlorination activity in the vicinity of well PW4. These findings demonstrate that biostimulation with NH4 + can enhance Dhc reductive dechlorination rates; however, a "do nothing" approach that relies on indigenous diazotrophs can achieve similar dechlorination end points and avoids the potential for stalled dechlorination due to inhibitory levels of NH4 + or transformation products (i.e., nitrous oxide).
AB - Biostimulation to promote reductive dechlorination is widely practiced, but the value of adding an exogenous nitrogen (N) source (e.g., NH4 +) during treatment is unclear. This study investigates the effect of NH4 + availability on organohalide-respiring Dehalococcoides mccartyi (Dhc) growth and reductive dechlorination in enrichment cultures derived from groundwater (PW4) and river sediment (TC) impacted with chlorinated ethenes. In PW4 cultures, the addition of NH4 + increased cis-1,2-dichloroethene (cDCE)-to-ethene dechlorination rates about 5-fold (20.6 ± 1.6 versus 3.8 ± 0.5 μM Cl- d-1), and the total number of Dhc 16S rRNA gene copies were about 43-fold higher in incubations with NH4 + ((1.8 ± 0.9) × 108 mL-1) compared to incubations without NH4 + ((4.1 ± 0.8) × 107 mL-1). In TC cultures, NH4 + also stimulated cDCE-to-ethene dechlorination and Dhc growth. Quantitative polymerase chain reaction (qPCR) revealed that Cornell-type Dhc capable of N2 fixation dominated PW4 cultures without NH4 +, but their relative abundance decreased in cultures with NH4 + amendment (i.e., 99 versus 54% of total Dhc). Pinellas-type Dhc incapable of N2 fixation were responsible for cDCE dechlorination in TC cultures, and diazotrophic community members met their fixed N requirement in the medium without NH4 +. Responses to NH4 + were apparent at the community level, and N2-fixing bacterial populations increased in incubations without NH4 +. Quantitative assessment of Dhc nitrogenase genes, transcripts, and proteomics data linked Cornell-type Dhc nifD and nifK expression with fixed N limitation. NH4 + additions also demonstrated positive effects on Dhc in situ dechlorination activity in the vicinity of well PW4. These findings demonstrate that biostimulation with NH4 + can enhance Dhc reductive dechlorination rates; however, a "do nothing" approach that relies on indigenous diazotrophs can achieve similar dechlorination end points and avoids the potential for stalled dechlorination due to inhibitory levels of NH4 + or transformation products (i.e., nitrous oxide).
UR - http://www.scopus.com/inward/record.url?scp=85075678214&partnerID=8YFLogxK
U2 - 10.1021/acs.est.9b04463
DO - 10.1021/acs.est.9b04463
M3 - Article
C2 - 31693350
AN - SCOPUS:85075678214
SN - 0013-936X
VL - 53
SP - 14548
EP - 14558
JO - Environmental Science and Technology
JF - Environmental Science and Technology
IS - 24
ER -