Effect of different carbon substrates on nitrate stable isotope fractionation during microbial denitrification.
Effect of different carbon substrates on nitrate stable isotope fractionation during microbial denitrification.
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DOI：
10.1021/es204075b
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发表时间：
2012-04
影响因子：
11.4
通讯作者：
A. Wunderlich;R. Meckenstock;F. Einsiedl
中科院分区：
文献类型：
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作者：
A. Wunderlich;R. Meckenstock;F. Einsiedl
在批量实验中，我们研究了溶解态硝酸盐在树枝化过程中N和O的同位素分馏。以乙酸盐、苯甲酸盐和甲苯为碳源，在严格厌氧条件下培养反硝化菌Thauera aromatica和Aromatoleum aromaticum菌株EbN1。（18）在微观实验中加入o标记水和（18）o标记亚硝酸盐，研究假设的亚硝酸盐与硝酸盐的反反应对稳定同位素分馏的影响。我们没有发现反向反应的证据。稳定同位素富集因子ε随碳源类型的不同而显著变化。甲苯(ε(15)N, -18.1±0.6‰到-7.3±1.4‰;ε(18)O, -16.5±0.6‰-16.1±1.5‰)和苯甲酸(ε(15)N, -18.9±1.3‰;ε（15)N, -23.5±1.9‰~ -22.1±0.8‰，ε(18)O, -15.9±1.1‰）的负同位素富集系数小于醋酸盐（ε(15)N, -23.5±1.9‰~ -22.1±0.8‰）；ε(18) 0, -23.7±1.8‰~ -19.9±0.8‰)。所观察到的同位素效应不依赖于生长动力学，这三种类型的电子供体是相似的。我们认为，不同的碳源通过改变硝酸盐在细胞壁上运输的相对动力学来改变观察到的同位素富集因子，而不是通过改变微生物反硝化的细胞内硝酸盐还原步骤的动力学。
In batch experiments, we studied the isotope fractionation in N and O of dissolved nitrate during dentrification. Denitrifying strains Thauera aromatica and "Aromatoleum aromaticum strain EbN1" were grown under strictly anaerobic conditions with acetate, benzoate, and toluene as carbon sources. (18)O-labeled water and (18)O-labeled nitrite were added to the microcosm experiments to study the effect of putative backward reactions of nitrite to nitrate on the stable isotope fractionation. We found no evidence for a reverse reaction. Significant variations of the stable isotope enrichment factor ε were observed depending on the type of carbon source used. For toluene (ε(15)N, -18.1 ± 0.6‰ to -7.3 ± 1.4‰; ε(18)O, -16.5 ± 0.6‰ to -16.1 ± 1.5‰) and benzoate (ε(15)N, -18.9 ± 1.3‰; ε(18)O, -15.9 ± 1.1‰) less negative isotope enrichment factors were calculated compared to those derived from acetate (ε(15)N, -23.5 ± 1.9‰ to -22.1 ± 0.8‰; ε(18)O, -23.7 ± 1.8‰ to -19.9 ± 0.8‰). The observed isotope effects did not depend on the growth kinetics which were similar for the three types of electron donors. We suggest that different carbon sources change the observed isotope enrichment factors by changing the relative kinetics of nitrate transport across the cell wall compared to the kinetics of the intracellular nitrate reduction step of microbial denitrification.