title: Carbon and nitrogen isotope effects associated with the dioxygenation of aniline and diphenylamine.
abstract: Dioxygenation of aromatic rings is frequently the initial step of biodegradation of organic subsurface pollutants. This process can be tracked by compound-specific isotope analysis to assess the extent of contaminant transformation, but the corresponding isotope effects, especially for dioxygenation of N-substituted, aromatic contaminants, are not well understood. We investigated the C and N isotope fractionation associated with the biodegradation of aniline and diphenylamine using pure cultures of Burkholderia sp. strain JS667, which can biodegrade both compounds, each by a distinct dioxygenase enzyme. For diphenylamine, the C and N isotope enrichment was normal with ε(C)- and ε(N)-values of -0.6 ± 0.1‰ and -1.0 ± 0.1‰, respectively. In contrast, N isotopes of aniline were subject to substantial inverse fractionation (ε(N) of +13 ± 0.5‰), whereas the ε(C)-value was identical to that of diphenylamine. A comparison of the apparent kinetic isotope effects for aniline and diphenylamine dioxygenation with those from abiotic oxidation by manganese oxide (MnO(2)) suggest that the oxidation of a diarylamine system leads to distinct C-N bonding changes compared to aniline regardless of reaction mechanism and oxidant involved. Combined evaluation of the C and N isotope signatures of the contaminants reveals characteristic Δδ(15)N/Δδ(13)C-trends for the identification of diphenylamine and aniline oxidation in contaminated subsurfaces and for the distinction of aniline oxidation from its formation by microbial and/or abiotic reduction of nitrobenzene.
authors.affiliation: Eawag, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland.
authors.forename: Sarah G
authors.initials: SG
authors.lastname: Pati
authors.forename: Kwanghee
authors.initials: K
authors.lastname: Shin
authors.forename: Marita
authors.initials: M
authors.lastname: Skarpeli-Liati
authors.forename: Jakov
authors.initials: J
authors.lastname: Bolotin
authors.forename: Soren N
authors.initials: SN
authors.lastname: Eustis
authors.forename: Jim C
authors.initials: JC
authors.lastname: Spain
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Hofstetter
mesh_terms: D000814:Aniline Compounds / Q000737:chemistry / Q000378:metabolism*; D001673:Biodegradation, Environmental; D019117:Burkholderia / Q000378:metabolism*; D002247:Carbon Isotopes; D049308:Dioxygenases / Q000378:metabolism; D004159:Diphenylamine / Q000737:chemistry / Q000378:metabolism*; D017895:Manganese Compounds / Q000737:chemistry; D009587:Nitrogen Isotopes; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry; D012989:Soil Pollutants / Q000737:chemistry / Q000378:metabolism
chemical_list: D000814:Aniline Compounds; D002247:Carbon Isotopes; D017895:Manganese Compounds; D009587:Nitrogen Isotopes; D010087:Oxides; D012989:Soil Pollutants; C027424:manganese oxide; D004159:Diphenylamine; D049308:Dioxygenases; C023650:aniline