N and O Isotope Fractionation in Nitrate during Chemolithoautotrophic Denitrification by Sulfurimonas gotlandica

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• 作者：Claudia Frey ; Susanna Hietanen ; Klaus J眉rgens ; Matthias Labrenz ; Maren Voss
• 刊名：Environmental Science & Technology
• 出版年：2014
• 出版时间：November 18, 2014
• 年：2014
• 卷：48
• 期：22
• 页码：13229-13237
• 全文大小：389K
• ISSN：1520-5851

文摘

Chemolithoautotrophic denitrification is an important mechanism of nitrogen loss in the water column of euxinic basins, but its isotope fractionation factor is not known. Sulfurimonas gotlandica GD1p>Tp>, a recently isolated bacterial key player in Baltic Sea pelagic redoxcline processes, was used to determine the isotope fractionation of nitrogen and oxygen in nitrate during denitrification. Under anoxic conditions, nitrate reduction was accompanied by nitrogen and oxygen isotope fractionation of 23.8 卤 2.5鈥?and 11.7 卤 1.1鈥? respectively. The isotope effect for nitrogen was in the range determined for heterotrophic denitrification, with only the absence of stirring resulting in a significant decrease of the fractionation factor. The relative increase in 未p>18p>O_NO3 to 未p>15p>N_NO3 did not follow the 1:1 relationship characteristic of heterotrophic, marine denitrification. Instead, 未p>18p>O_NO3 increased slower than 未p>15p>N_NO3, with a conserved ratio of 0.5:1. This result suggests that the periplasmic nitrate reductase (Nap) of S. gotlandica strain GD1p>Tp> fractionates the N and O in nitrate differently than the membrane-bound nitrate reductase (Nar), which is generally prevalent among heterotrophic denitrifiers and is considered as the dominant driver for the observed isotope fractionation. Hence in the Baltic Sea redoxcline, other, as yet-unidentified factors likely explain the low apparent fractionation.