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Isotope analysis as a natural reaction probe to determine mechanisms of biodegradation of 1,2‐dichloroethane
Author(s) -
Hirschorn Sarah K.,
DinglasanPanlilio M. Joyce,
Edwards Elizabeth A.,
LacrampeCouloume Georges,
Sherwood Lollar Barbara
Publication year - 2007
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/j.1462-2920.2007.01282.x
Subject(s) - biodegradation , isotope analysis , fractionation , environmental chemistry , degradation (telecommunications) , isotope fractionation , electron acceptor , kinetic isotope effect , isotopes of carbon , isotope , stable isotope ratio , chemistry , chromatography , total organic carbon , biology , organic chemistry , deuterium , ecology , physics , quantum mechanics , computer science , telecommunications
Summary 1,2‐Dichloroethane (1,2‐DCA), a chlorinated aliphatic hydrocarbon, is a well‐known groundwater contaminant. In this study, fractionation of stable carbon isotope values of 1,2‐DCA during biodegradation was used as a novel reaction probe to provide information about the mechanism of 1,2‐DCA biodegradation under both aerobic (O 2 ‐reducing) and anaerobic (NO 3 ‐reducing) conditions. Under O 2 ‐reducing conditions, an isotopic enrichment value ( ε ) of −25.8 ± 1.1‰ (±95% confidence intervals) was measured for the enrichment culture. Under NO 3 ‐reducing conditions, an ε ‐value of −25.8 ± 3.5‰ was measured. The microbial culture produced isotopic enrichment values ( ε ) that are not only large and reproducible, but also are the same whether O 2 or NO 3 was used as an electron acceptor. Combining data measured under both O 2 ‐ and NO 3 ‐reducing conditions, an isotopic enrichment value ( ε ) of −25.8 ± 1.6‰ is measured for the microbial culture during 1,2‐DCA degradation. The ε ‐value can be converted into a kinetic isotope effect (KIE) value to relate the observed isotopic fractionation to the mechanism of degradation. This KIE value (1.05) is consistent with degradation via hydrolytic dehalogenation under both electron‐accepting conditions. This study demonstrates the added value of compound‐specific isotope analysis not only as a technique to verify the occurrence and extent of biodegradation in the field, but also as a natural reaction probe to provide insight into the enzymatic mechanism of contaminant degradation.