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Applied and Environmental Microbiology, January 1999, p. 163-168, Vol. 65, No. 1
Department of Chemical and Materials
Engineering, University of Alberta, Edmonton, Alberta, T6G
2G6,1 and
Department of Biological
Sciences, University of Alberta, Edmonton, Alberta, T6G
2E9,2 Canada
Received 8 July 1998/Accepted 19 October 1998
It has been proposed that addition of surfactants to contaminated
soil enhances the solubility of target compounds; however, surfactants
may simultaneously reduce the adhesion of bacteria to hydrophobic
surfaces. If the latter mechanism is important for the biodegradation
of virtually insoluble contaminants, then the use of surfactants may
not be beneficial. The adhesion of a Mycobacterium strain
and a Pseudomonas strain, isolated from a
creosote-contaminated soil, to the surfaces of highly viscous non-aqueous-phase liquids (NAPLs) was measured. The NAPLs were organic
material extracted from soils from two creosote-contaminated sites and
two petroleum-contaminated sites. Cells suspended in media with and
without surfactant were placed in test tubes coated with an NAPL, and
the percentages of cells that adhered to the surface of the NAPL in the
presence and absence of surfactant were compared by measuring optical
density. Test tubes without NAPLs were used as controls. The presence
of either Triton X-100 or Dowfax 8390 at a concentration that was
one-half the critical micelle concentration (CMC) inhibited adhesion of
both species of bacteria to the NAPLs. Both surfactants, when added at
concentrations that were one-half the CMCs to test tubes containing
previously adhered bacteria, also promoted the removal of the cells
from the surfaces of the NAPL-coated test tubes. Neither surfactant was
toxic to the bacteria. Further investigation showed that a low
concentration of surfactant also inhibited the growth of both species
on anthracene, indicating that the presence of a surfactant resulted in
a reduction in the uptake of the solid carbon source.
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Bacterial Adhesion to Soil Contaminants in the
Presence of Surfactants
*
Corresponding author. Mailing address: Department of
Chemical and Materials Engineering, 536 Chemical-Mineral Engineering Building, University of Alberta, Edmonton, Alberta T6G 2G6, Canada. Phone: (403) 492-7965. Fax: (403) 492-2881. E-mail:
Murray.Gray{at}ualberta.ca.
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