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Appl. Environ. Microbiol., Sep 1995, 3329-3335, Vol 61, No. 9
JW Barton and RM Ford
A well-characterized experimental system was designed to evaluate the
effect of porous media on macroscopic transport coefficients which are used
to characterize the migration of bacterial populations. Bacterial density
profiles of Pseudomonas putida PRS2000 were determined in the presence and
absence of a chemical attractant (3-chlorobenzoate) gradient within sand
columns having a narrow distribution of particle diameters. These
experimental profiles were compared with theoretical predictions to
evaluate the macroscopic transport coefficients. The effective random
motility coefficient, used to quantify migration due to a random process in
a porous medium, decreased nearly 20-fold as grain size in the columns
decreased from 800 to 80 (mu)m. The effective random motility coefficient
(mu)(infeff) was related to the random motility coefficient (mu), measured
in a bulk aqueous system, according to (mu)(infeff) = ((epsilon)/(tau))(mu)
with porosity (epsilon) and tortuosity (tau). Over the times and distances
examined in these experiments, bacterial density profiles were unaffected
by the presence of an attractant gradient. Theoretical profiles with the
aqueous phase value of the chemotactic sensitivity coefficient (used to
quantify migration due to a directed process) were consistent with this
result and suggested that any chemotactic effect on bacterial migration was
below the detection limits of our assay.
Copyright © 1995, American Society for Microbiology
Determination of Effective Transport Coefficients for Bacterial Migration in Sand Columns
Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia 22903
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