Anaerobic biodegradation of n-hexadecane by a nitrate-reducing consortium

Abstract

Nitrate-reducing enrichments, amended with n-hexadecane, were established with petroleum-contaminated sediment from Onondaga Lake. Cultures were serially diluted to yield a sediment-free consortium. Clone libraries and denaturing gradient gel electrophoresis analysis of 16S rRNA gene community PCR products indicated the presence of uncultured alpha- and betaproteobacteria similar to those detected in contaminated, denitrifying environments. Cultures were incubated with H 34-hexadecane, fully deuterated hexadecane (d 34hexadecane), or H 34-hexadecane and NaH 13CO 3. Gas chromatography-mass spectrometry analysis of silylated metabolites resulted in the identification of [H 29] pentadecanoic acid, [H 25] tridecanoic acid, [1- 13C] pentadecanoic acid, [3- 13C]heptadecanoic acid, [3- 13C]10-methylheptadecanoic acid, and d 27-pentadecanoic, d 25-, and d 24-tridecanoic acids. The identification of these metabolites suggests a carbon addition at the C-3 position of hexadecane, with subsequent β-oxidation and transformation reactions (chain elongation and C-10 methylation) that predominantly produce fatty acids with odd numbers of carbons. Mineralization of [l- 14C]hexadecane was demonstrated based on the recovery of 14CO 2 in active cultures. Copyright © 2009, American Society for Microbiology. All Rights Reserved.