Isotope Fractionation Associated with the Biodegradation of 2- and 4‑Nitrophenols via Monooxygenation Pathways

• Published in: Environmental science & technology Vol. 47; no. 24; pp. 14185 - 14193
• Main Authors: Wijker, Reto S, Kurt, Zohre, Spain, Jim C, Bolotin, Jakov, Zeyer, Josef, Hofstetter, Thomas B
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 17.12.2013
• Subjects: Applied sciences; Arthrobacter - metabolism; Bacillus; Bacillus - metabolism; Benzoquinones - chemistry; Benzoquinones - metabolism; Biocatalysis; Biodegradation; Biodegradation, Environmental; Biological and physicochemical phenomena; Biological and physicochemical properties of pollutants. Interaction in the soil; Carbon Isotopes; Cells; Chemical Fractionation; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Environmental Pollutants - analysis; Environmental science; Enzymes; Exact sciences and technology; Fractionation; Isotopes; Kinetics; Metabolic Networks and Pathways; Mixed Function Oxygenases - metabolism; Natural water pollution; Nitrogen Isotopes; Nitrophenols - chemistry; Nitrophenols - metabolism; Phenols; Pollutants; Pollution; Pollution, environment geology; Pseudomonas; Pseudomonas putida; Pseudomonas putida - metabolism; Soil and sediments pollution; Water treatment and pollution; Biodegradation; Isotopic analysis; Nitro compound; Pollutant behavior; Nitrogen isotopes; Metabolic pathway; Soil pollution; Carbon isotopes; Selfpurification; Reaction mechanism; Phenols; Isotopic fractionation; Aromatic compound; Water pollution; Organic compounds
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es403876u

Monooxygenation is an important route of nitroaromatic compound (NAC) biodegradation and it is widely found for cometabolic transformations of NACs and other aromatic pollutants. We investigated the C and N isotope fractionation of nitrophenol monooxygenation to complement the characterization of NAC (bio)degradation pathways by compound-specific isotope analysis (CSIA). Because of the large diversity of enzymes catalyzing monooxygenations, we studied the combined C and N isotope fractionation and the corresponding 13C- and 15N-apparent kinetic isotope effects (AKIEs) of four nitrophenol-biodegrading microorganisms (Bacillus spharericus JS905, Pseudomonas sp. 1A, Arthrobacter sp. JS443, Pseudomonas putida B2) in the pH range 6.1–8.6 with resting cells and crude cell extracts. While the extent of C and N isotope fractionation and the AKIE-values varied considerably for the different organisms, the correlated C and N isotope signatures (δ15N vs δ13C) revealed trends, indicative of two distinct monooxygenation pathways involving hydroxy-1,4-benzoquinone or 1,2- and 1,4-benzoquinone intermediates, respectively. The distinction was possible based on larger secondary 15N-AKIEs associated with the benzoquinone pathway. Isotope fractionation was neither masked substantially by nitrophenol speciation nor transport across cell membranes. Only when 4-nitrophenol was biodegraded by Pseudomonas sp. 1A did isotope fractionation become negligible, presumably due to rate-limiting substrate binding steps pertinent to the catalytic cycle of flavin-dependent monooxygenases.