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Applied and Environmental Microbiology, July 2000, p. 2959-2964, Vol. 66, No. 7
Department of Land Resources and
Environmental Sciences, Montana State University, Bozeman, Montana
59717-3120
Received 11 January 2000/Accepted 5 May 2000
We analyzed the impact of surfactant addition on hydrocarbon
mineralization kinetics and the associated population shifts of
hydrocarbon-degrading microorganisms in soil. A mixture of radiolabeled
hexadecane and phenanthrene was added to batch soil vessels. Witconol
SN70 (a nonionic, alcohol ethoxylate) was added in concentrations that
bracketed the critical micelle concentration (CMC) in soil (CMC')
(determined to be 13 mg g
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Molecular Analysis of Surfactant-Driven Microbial
Population Shifts in Hydrocarbon-Contaminated Soil
1). Addition of the
surfactant at a concentration below the CMC' (2 mg g
1)
did not affect the mineralization rates of either hydrocarbon. However,
when surfactant was added at a concentration approaching the CMC' (10 mg g
1), hexadecane mineralization was delayed and
phenanthrene mineralization was completely inhibited. Addition of
surfactant at concentrations above the CMC' (40 mg g
1)
completely inhibited mineralization of both phenanthrene and hexadecane. Denaturing gradient gel electrophoresis of 16S rRNA gene
segments showed that hydrocarbon amendment stimulated
Rhodococcus and Nocardia populations that were
displaced by Pseudomonas and Alcaligenes
populations at elevated surfactant levels. Parallel cultivation studies
revealed that the Rhodococcus population can utilize
hexadecane and that the Pseudomonas and
Alcaligenes populations can utilize both Witconol SN70 and
hexadecane for growth. The results suggest that surfactant applications
necessary to achieve the CMC alter the microbial populations
responsible for hydrocarbon mineralization.
*
Corresponding author. Mailing address: Department of
Land Resources and Environmental Sciences, P.O. Box 173120, Montana
State University, Bozeman, MT 59717-3120. Phone: (406) 994-5077. Fax: (406) 994-3933. E-mail: binskeep{at}montana.edu.
Journal Series number 2000-33 of the Montana Agricultural
Experiment Station.
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