Impact of Fixed Nitrogen Availability on Dehalococcoides mccartyi Reductive Dechlorination Activity
Impact of Fixed Nitrogen Availability on Dehalococcoides mccartyi Reductive Dechlorination Activity
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DOI：
10.1021/acs.est.9b04463
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发表时间：
2019-12-17
影响因子：
11.4
通讯作者：
Loffler, Frank E.
中科院分区：
文献类型：
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作者：
Kaya, Devrim;Kjellerup, Birthe V.;Loffler, Frank E.
促进还原脱氯的生物刺激被广泛应用，但在处理过程中添加外源氮(N)源(如NH4+)的价值尚不清楚。研究了NH4+有效性对含氯乙烯影响的地下水(PW4)和河流沉积物(TC)富集菌中有机卤化物呼吸的麦卡氏球菌(DHC)生长和还原脱氯的影响。在PW4培养中，添加NH4+使顺式-1，2-二氯乙烯(CDCE)对乙烯的脱氯率提高了约5倍(20.6+/-1.6比3.8+/-0.5mCld(-1))，与不加NH4+培养((4.1+/-0.8)x10(7)mL(-1))相比，加入NH4+培养的DHC 16S rRNA基因拷贝数增加了约43倍。在TC培养中，NH4+还促进了cDCE到乙烯的脱氯和DHC生长。定量聚合酶链式反应(QPCR)显示，在没有NH4+的情况下，能够固定N-2的康奈尔型DHC在PW4培养中占主导地位，但在NH4+修饰的培养中，它们的相对丰度降低(即占总DHC的99%比54%)。半夏不能固定N-2的DHC负责TC培养物中cDCE的脱氯，而重氮营养群落成员在无NH4+的条件下满足了他们固定的N需求。在群落水平上对NH4+有明显的响应，无NH4+培养时固氮细菌数量增加。定量评估DHC固氮酶基因、转录本和蛋白质组学数据将康奈尔型DHC nifD和nifK的表达与固定的N限制联系在一起。NH4+的加入对PW4井附近DHC的原位脱氯活性也有积极的影响。这些发现表明，NH4+的生物刺激可以提高DHC的还原脱氯率；然而，依赖本土重氮菌的“无所作为”方法可以达到类似的脱氯终点，并避免由于NH4+或转化产物(即一氧化二氮)的抑制水平而导致脱氯停滞的可能性。
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 mu M 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) x 10(8) mL(-1)) compared to incubations without NH4+ ((4.1 +/- 0.8) x 10(7) 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 N-2 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 N-2 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 N-2-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).